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PAL Questions: 854 - Garden Tools: 352 - Recommended Websites: 638

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Keywords: Blechnum spicant, Acorus, Adiantum pedatum, Carex, House plants

PAL Question:

I've taken up planning plants for our office, and wondered if you could give advice. I'm looking for Northwest native plants that would be happy indoors, in an office environment. Available sunlight will vary by spot but is generally low (but I can probably swing some plant lights); air is standard low-humidity commercial-building air.

View Answer:

Most Northwest native plants I can think of are not ideal for growing indoors. However, I asked my colleague who used to garden for the Seattle Public Library, and she says that the library is growing native species of ferns indoors. She notes that they are especially prone to pests (whitefly) and diseases (scale), and must be watered every day.

Below is the list of plants being grown in the main (Central) library branch:

  • Acorus
  • Blechnum spicant
  • Adiantum pedatum
  • Carex elata 'Bowles Golden'(tall)
  • other fern (Rumohra adiantiformis?)

I hope this helps. If you wish to reconsider using natives in favor of more traditional choices for indoor plants, there are many more choices available. Below are a few links that may be use to you:

Low Light Houseplants from University of Vermont Extension

Growing Indoor Plants with Success from University of Georgia Cooperative Extension

Interior Plants: Selection and Care from University of Arizona Cooperative Extension

Season All Season
Date 2007-06-08
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Keywords: Moss gardening, Mosses, Lawn alternatives

PAL Question:

Could you tell me how to replace grass with moss in the shady areas of our lawn?

View Answer:

There are a number of options for replacing the grass in the shady part of your garden. Should you decide to cultivate moss, Oregon State University's page on Encouraging Mosses should be of interest.

There are two books I would recommend, Moss Gardening by George Schenk (Timber Press, 1997), particularly the chapter on "Moss Carpets," and How to Get Your Lawn Off Grass by Carole Rubin (Harbour Publishing, 2002). Rubin gives directions for preparing your site, which involve digging out existing plants or smothering the lawn with mulches of leaves (12 inches), bark (3 inches), or newspaper (10 sheets thick). Schenk offers several different methods for creating a moss garden. Briefly paraphrasing, these are:

  1. Work with nature, allowing self-sown spores of moss to take hold. (Prepare the site by weeding, raking, and perhaps rolling the surface smooth).
  2. Encourage the moss in an existing lawn by weeding out grass. You can plant what the author calls "weed mosses" which will spread, such as Atrichum, Brachythecium, Calliergonella, Mnium, Plagiothecium, Polytrichum, and others.
  3. Instant carpet: you can moss about 75 square feet if you have access to woods from which large amounts of moss can be removed legally.
  4. Plant moss sods at spaced intervals (about one foot apart) and wait for them to grow into a solid carpet.Choose plants that match your soil and site conditions.
  5. Grow a moss carpet from crumbled fragments. This is rarely done, and only a few kinds of moss will grow this way, including Leucobryum, Racomitrium, and Dicranoweisia.

In her book Big Ideas for Northwest Small Gardens, Marty Wingate recommends Mazus reptans. It is semi-evergreen to evergreen with tiny blue flowers from late spring through summer. It takes full sun to part shade and is delicate looking, but takes foot traffic. It requires some fertilizer to stay perky. Another source of ideas is the website www.stepables.com. Click on "plant info," then "plant search."

Another ground cover that can take foot traffic is Leptinella gruveri "Miniature Brass Buttons."

Season All Season
Date 2007-06-08
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Keywords: Clematis

PAL Question:

I have a beautiful clematis in full bloom right now. Do I need to dead head the spent blooms to make it bloom again? It is Clematis Candida.

View Answer:

In researching this question, I used Raymond Evison's excellent 1998 book, The Gardener's Guide to Growing Clematis. Your Clematis lanuginosa 'Candida' is considered a mid-season, large-flowered type, and it often reblooms, according to Evison. In the chapter on cultivation, he says, "Some clematis growers prefer to remove spent flowerheads to encourage further crops of flowers, especially with the early large-flowered single, double, and semi-double clematis. Certainly, if the old flowers are removed with a length of stem with 2-3 nodes, new growth will appear and a further crop of flowers will be produced. When this is done, it is important to keep the clematis well watered and fed. The only drawback...is that the attractive seedheads on this group of clematis will be lost. A compromise can be achieved by removing only 50 per cent of the spent flowerheads..."

Season Summer
Date 2007-06-11
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Keywords: Zamia, Poisonous plants, House plants, Cycads

PAL Question:

I am interested in finding out if someone there can tell me the proper culture for Zamia furfuracea. I just acquired one that had been potted up as a bonsai and put on sale at a local grocery store. I think they may not have known or cared what it was. This is a plant I grew outdoors when I lived in California. I'm wondering what to do with it in Vancouver, WA. The options are greenhouse, patio pot, indoors, outdoors.

View Answer:

I found general cultural information from Florida State University Cooperative Extension. This is a zone 9b-11 plant, and your area is probably about zone 8, so I think you would want to grow this with some protection.

University of British Columbia Botanical Garden's discussion forum describes this as an indoor plant. This article in the journal of University of Arizona Cooperative Extension is about a similar plant, Zamioculcas zamiifolia, often confused with Zamia furfuracea.

Richard Langer's book, Grow It Indoors (Stackpole Books, 1995) says to grow this "handy table-sized cycad" in temperate partial sun with humusy soil that is kept constantly moist.

Another thing to keep in mind if you are growing this plant around pets or small children is its toxicity. The ASPCA lists this plant as toxic. Dr. Nelson's Veterinary Blog has an article entitled "Sago palms are poisonous to animals."

Season All Season
Date 2007-06-08
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Keywords: Tsuga heterophylla, Trees--Diseases and pests

PAL Question:

My Western Hemlock is infested with woolly adelgid. Help! How can I save my tree?

View Answer:

The USDA Forest Service has an entire web site devoted to this pest problem, and includes information on different ways of managing the Hemlock woolly adelgid.

The most effective approach is prevention, as treatment tends to be expensive and is not always effective. Information from University of Maryland Extension does describe the use of dormant oil spray in late winter and summer application of horticultural oil and insecticidal soap, but care must be taken to cover the entire tree. Also, it is important to avoid the use of nitrogen-heavy fertilizers which create a lot of succulent new growth attractive to the pest.

I recommend that you consult a certified arborist for advice on how to save your (Western hemlock). You can obtain referrals from Plant Amnesty or you can select an arborist from the Pacific Northwest Chapter of the International Society of Arboriculture.

Season All Season
Date 2007-06-13
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Keywords: Prunus, Fruit--Diseases and pests

PAL Question:

For three years, my plum tree has had leaves that curl and shrivel somewhat. I have heard of aphids causing leaf curl in plums, but I don't see many aphids.

I also have a peach tree that has "Peach Leaf Curl" or Taphrina deformans and the symptoms on the plum leaves look similar to that. Here is what I wonder:

  • The peach and plum are at least 100 yards apart. Is it really possible that the peach infected the plum?
  • With the peach tree the fruits are also affected but with the plum fruits do not appear to be affected.
  • Are peach and plum affected by the same diseases?

View Answer:

Both peach and plum trees are in the genus Prunus. Your plum tree's problem sounds like plum pockets and peach leaf curl, which are caused by fungus (usually Taphrina).

From Iowa State University Plant Pathology:
Have you noticed lately that your peach leaves appear curled or puckered? Do leaves appear to be lighter than normal, flushed with red, blistered, distorted, and curled? Chances are your tree has peach leaf curl, a fungal disease caused by Taphrina deformans. Although peach leaf curl is primarily a disease of peach, nectarines are also affected. Peach leaf curl is first noticed in spring when young leaves start to emerge. The entire leaf or a portion of it may appear crinkled and curled with flushes of red or purple . Later on in the season, the fungus begins to produce spores and leaves appear silvery or powdery gray. Infected leaves turn yellow and brown and fall off the tree and are replaced by a new set of foliage. Flowers, young fruits and stems may also be infected. Affected fruits are distorted with wrinkled, discolored areas on the surface. Extensive defoliation may affect fruit yield the following year and may also predispose the tree to winter injury and other diseases.

Plum pocket is a disease in plums caused by Taphrina communis. Leaf symptoms are similar with peach leaf curl and the plums appear to be distorted, wrinkled, and puffy. This disease is not considered a serious problem in most commercially cultivated plum varieties.

Here is Oregon State University's online guide to plant diseases. This is Washington State University's comparable site.

I don't know if your plum could have gotten the same species of Taphrina fungus that is affecting your peach (i.e., Taphrina deformans), but the conditions in our climate are probably ideal for this type of fungal disease. University of California, Davis says that the pathogen which causes peach leaf curl survives on tree surfaces and buds, and is enhanced by wet spring weather.

From University of Nebraska Plant Pathology:

Plum Pockets is very similar to the well-known disease peach leaf curl. It reached epidemic proportions on plum in the 1880's and sand cherry in the 1940's. The disease is still common today but rarely has an economic impact on stone fruit production. However, its unique symptoms always seem to peak the interest of individuals who are seeing it for the first time. The disease is caused by two species of Taphrina. Taphrina communis (Sadelbeck) Giesenh. has a worldwide distribution. Its hosts include plum (Prunus angustifolia) and several wild Prunus spp. found in America. Taphrina pruni primarily infects European plums and is rarely found in America. The disease cycle of Taphrina communis is similar to that of Taphrina deformans (peach leaf curl). The fungus overwinters as conidia on twigs and bud scales. Infection generally begins at bud break when these spores are rain splashed to susceptible green tissue. Leaves, shoots, and fruit are all susceptible but symptom development is most common on fruit. The fungus invades host tissue directly through epidermal cells. Once the fungus is established, a specialized mat of fungal cells (hymeneal layer) containing asci and ascospores forms. The asci are not protected by a specialized ascocarp. Ascospores are released, germinate and begin budding, much as a yeast does. Conidia (bud conidia) serve as secondary inoculum in the spread of the disease. Initiation of the disease cycle is favored by cool wet weather.

You might consider bringing in samples of the affected leaves to a Master Gardener Clinic for a definitive diagnosis. They may also have more information on whether the disease can pass from peach to plum, or whether your two types of trees simply have two different strains of the pathogen.

Season All Season
Date 2007-06-13
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Keywords: Chenopodium quinoa

PAL Question:

What is quinoa, botanically? Is it a grain, or something else?

View Answer:

The botanical name for Quinoa is Chenopodium quinoa. According to information from the Alternative Crops Manual produced by University of Wisconsin Extension, it is an annual plant in the goosefoot or Amaranthaceae family, which also includes the familiar weed, lambs' quarters or Chenopodium album. This article states that "Quinoa is sometimes referred to as a 'pseudocereal' because it is a broadleaf non-legume that is grown for grain unlike most cereal grains which are grassy plants. It is similar in this respect to the pseudocereals buckwheat and amaranth." Edible: An illustrated guide to the world's food plants (National Geographic, 2008) states that true cereals are members of the Poaceae or grass family, but quinoa more closely resembles spinach. It was first used as a food plant around 5000 B.C.E. near Lake Titicaca in the Andes, where it is native. Its common name in that region is "the mother grain."

Incidentally, the Food and Agriculture Organization of the United Nations declared 2013 the International Year of Quinoa, "recognizing the Andean indigenous peoples, who have maintained, controlled, protected and preserved quinoa as food for present and future generations thanks to their traditional knowledge and practices of living well in harmony with mother earth and nature."

Season All Season
Date 2013-03-13
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Keywords: Cucumis melo, Cross-pollination, Citrullus lanatus, Cucumis sativus

PAL Question:

Will watermelon and cantaloupe cross-pollinate and produce bad-tasting melons? Is it possible for a vine that had cucumbers growing on it earlier in the season to produce a cantaloupe? I could swear that we now have what looks like a melon on a vine that had cukes before...

View Answer:

The short answer is, no. It's fine to grow watermelons and cantaloupe side by side. Cross-pollination between melon varieties may occur, but not between watermelons (Citrullus lanatus v. lanatus) and cantaloupes (Cucumis melo ssp. melo v. cantalupo), as they are two different species. In addition, cross-pollination affects not the melon produced that year, but the melons one might grow from any seeds produced inside that melon. According to Sue Stickland's Back Garden Seed Saving (Chelsea Green, 2001), "commercial seed growers are recommended to isolate melon varieties by 500-1000 meters" or "bag and hand-pollinate the flowers" to keep unwanted hybridization from happening.

The same principle holds true for cantaloupe (Cucumis melo and cucumber (Cucumis sativus): they are indeed in the same plant family (Cucurbitaceae), but they are different species. If your vines were planted close together, you night not have realized there was a melon developing in among the cucumbers--and if you planted the vines from seed, it's very possible the seed packet contained a surprise cantaloupe!

You may find this information from Iowa State University Extension about cross-pollination among vine crops interesting:
"Since they have a similar flowering habit, bloom about the same time, and are members of the same plant family, it is logical that gardeners might assume that squash, melons, and cucumbers will cross-pollinate. Fortunately, however, this is not true. The female flowers of each crop can be fertilized only by pollen from male flowers of the same species. Cross pollination, however, can occur between varieties within a species."

An article on fruit set in the Cucurbit family from University of California, Davis (which also has information on how to hand-pollinate plants when necessary) says much the same thing:
"A common misconception is that squash, melons, and cucumbers will cross-pollinate. This is not true; the female flowers of each can be fertilized only by pollen from that same species. Varieties within each species, however, will cross-pollinate."

Season All Season
Date 2012-05-10
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Keywords: Wisteria

PAL Question:

We have a Chinese Wisteria which we've had for 20 years. We've trained it on a trellis to the side of our covered porch and then on a rope across the front so there is a nice green, leafy fringe along the porch front. However, this plant has never bloomed.

We have consulted with our local horticultural experts and they have suggested various treatments. The lawn care people do not fertilize near the roots of the wisteria so it doesn't get too much phosphorus, we have done root pruning, we have even hit the trunk with a board to shock it, have applied super phosphate but no blooms. We get some pretty cold winters, but I've never even seen flower buds anywhere on the plant. I know wisterias are sometimes late in blooming, but this is a long time to wait! The roots of the plant face east and get lots of sun. The part across the porch is shaded in the afternoon because we have two pine trees in the front yard. We prune off the tendrils that form during the summer to keep the plant in check, but what else can we do to get blooms? I know it would be a spectacular display if it ever bloomed and have almost given up trying. I'm thinking of hanging artificial blooms just to get the effect!

View Answer:

I found quite a bit of discussion in online gardening forums about flowerless wisterias, so you are not alone. You may find this information from Cass Turnbull of Plant Amnesty helpful:

"THE MOST COMMON COMMENT I get at classes and at the PlantAmnesty educational booth is, "My wisteria won't bloom." It is natural for these vines to take between three and seven years to start blooming. I have read that frequent, proper pruning may help them to begin blooming sooner, or at least more. On the other hand, some people have old vines that have never bloomed. I am told that these are seed grown plants or "mules." I have often heard root pruning recommended to force an older vine to bloom. Basically, this means that you use your shovel to cut the roots in a circle (or dotted circle) a foot or two from the vine. I have also heard people recommend fertilizer formulated to encourage blooms, (not heavy on nitrogen). However, I have been faced with such a vine and had no luck with either technique. In that case, as with all non-performers, removal is the best option, and no one will blame you for it."

Here are gardener Ketzel Levine's comments, from her NPR.org site:

"Depending on how old your wisteria is, do know that young plants can take up to eight or ten years before they flower, especially if started from seed. Other reasons wisteria fail to bloom: lack of adequate sunlight (needs at least six hours of full sunlight); too much nitrogen fertilizer (causes more vegetative growth); pruned heavily in winter or spring (also encourages vigorous vegetative growth); severe winter injury/cold-blasted flower buds (though that is clearly not a problem this year) or a bum plant. It happens."

You could either try the method described above, of cutting a circle with a shovel, or you could replace the vine, or you could follow through on your artifical flower idea! (I've heard that Bellevue Botanical Gardens hangs Wisteria-shaped lights from their arbor for their holiday light show.)

Season Summer
Date 2007-06-13
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Keywords: Hippophae

PAL Question:

I am wondering about whether or not sea buckthorn grows here in Washington, if you have examples of it at the arboretum, or if anyone here sells the tree or the berries/extracts. A Ukrainian friend told me about the health benefits of the berries, and I was curious as to whether sea buckthorn can be found in Washington state.

View Answer:

Washington State University's Fruit Research Station in Mount Vernon has been growing sea buckthorn, or Hippophae rhamnoides, in its fruit trials. Below are the varieties they grew:

Sea Buckthorn (Seaberry)
'Frugana'
'Hergosa'
'Leikora'
'Pollmix' male
'Russian Orange'

Page 16 of this WSU publication includes the results of the trials:

"Sea Buckthorn (Hippophae rhamnoides) is a very thorny shrub or small tree native to eastern Europe and Asia. It has nitrogen fixing properties and is very tolerant of drought and poor soils, so has been introduced as a shelter belt plant in some of the plains States and Canada. In eastern Europe and the former Soviet Union the berries are commonly harvested for juice, which has nutritious and other healthful properties. Medicinal uses of extracted plant oils are also well documented in Europe and Asia. Plants on trial at Mount Vernon have fruited very successfully for the past 3 years, and appear quite well adapted horticulturally. The plants are very productive, setting many small orange fruits with a citrus like flavor. The juice is high in vitamin C. We have not had any problems with pests thus far and this shows great potential for organic growing. The commercial potential of this plant is being pursued by the British Columbia Sea Buckthorn Growers' Association, in the Okanagan Valley. Information on the Association and on sea buckthorn is available from Okanagan Sea Buckthorn. More information in a paper on the fruit potential of sea buckthorn by Thomas S.C. Li from the Summerland, B.C. fruit research station."

According to Arthur Lee Jacobson's Trees of Seattle (2006), there is a specimen in the Washington Park Arboretum, but it may be easier to locate the 19-foot example at the Good Shepherd Center on the south wall of the annex (see directions to Seattle Tilth) There are others at Meadowbrook Park, and individual residences at 4015 NE 70th St., and 208 NE 42nd St. You might also ask the manager of the U.W. Medicinal Herb Garden if he has grown it: Keith Possee, UW Medicinal Herb Garden 206-543-0436, 543-1126; kpossee@u.washington.edu.

From the Raintree Nursery catalog:

"Perhaps the most widely grown, northern hardy, fruiting plant in the world and most Americans have never heard of it. Incredibly productive and great for your backyard. This attractive small tree or shrub from the Russian Far East has narrow silver leaves. It grows from 6-10' tall with a narrow upright growth habit. Space 7' apart or 3-5' for a hedge. It is extremely hardy, to -50 F. It is disease resistant and easy to grow. Plentiful round yellow orange fruits cover the female plants making them beautiful edible ornamentals. Branches are used in florist displays. Commercial crops are harvested by cutting off entire fruit laden branches. Very high in Vitamin C, ln Europe the fruit is made into sauces or jellies and as a base of liqueurs. The juice is sour and has an orange passionfruit like flavor when sweetened. Blended with other fruits, or by itself, it makes a delicious juice. It is also used widely in Europe and Asia as a healing oil and for other medicinal purposes."

Season All Season
Date 2007-06-14
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Keywords: Chionodoxa, Vancouveria hexandra, Tiarella, Pulmonaria, Galium, Brunnera, Vinca, Epimedium, Lamium, Platanus, Narcissus, Liliaceae, Geranium

PAL Question:

We have a very large beautiful sycamore in our back yard. My roommate thought it would be nice to build a flower garden around the base of the tree, but something tells me that doing so would be harmful to the tree's root system. Is this true? I would love to hear your thoughts.

View Answer:

I think it should be safe to plant shallow-rooted, shade- and drought-tolerant perennials and small bulbs under your sycamore (I'm assuming you mean Platanus species, and not sycamore maple, which is Acer pseudoplatanus). You just need to be careful not to pile soil on top of any exposed roots, and try not to scrape or scuff any roots when you are planting. This tree does have spreading roots so they may extend out some distance. More information about the tree can be found on the pages of the U.S. Forest Service.

Some of the plants which may work well in your garden are:

Brunnera macrophylla
Epimedium
Galium odoratum
Geranium phaeum
Lamium (but not the invasive Lamium galeobdolon)
Pulmonaria
Tiarella
Vancouveria hexandra
Vinca minor
Chionodoxa
Narcissus
Scilla

Season All Season
Date 2007-06-16
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Keywords: Cryptomeria

PAL Question:

My Black Dragon Japanese Cedar has a lot of dead branches. The tree is healthy otherwise. A foot of new growth this year. The nursery told me this was normal. Can you give me an opinion?

View Answer:

Apparently, dieback is often seen on Cryptomeria, as the following information from North Carolina State University Cooperative Extension, no longer available online, suggests:

Cryptomeria can have leaf blight or spot. Branch dieback is common. Dieback has not been associated with a disease but has been touted as the nature of the tree. Pathologists are still researching this. There may be some tip dieback associated with a disease.

There is another discussion of a Cryptomeria with dead branches on University of British Columbia Botanical Garden's forum which mentions rust and needle blight (both fungal diseases) as possible causes.

You may want to bring samples of the affected branches (along with your photo) to a Master Gardener Clinic for diagnosis.

You may find this University of British Columbia Botanical Gardens Forum discussion of interest.

The growth rate of a foot a year makes sense, considering that this is not a large tree. See below what Great Plant Picks, a Seattle-based website, has to say about this tree. An earlier version of the page linked here, from Iseli Nursery, indicates a growth rate of only 3-6 inches a year.

Information from Iseli Nursery: Cryptomeria japonica 'Black Dragon' (Japanese cedar )
Cryptomeria japonica is one of the most variable conifers you can imagine, with plants ranging from very dwarf rounded shrubs, trees with golden or contorted leaves, and wild forest trees to 80 feet high and 20 feet wide. 'Black Dragon' takes the middle road, neither too small nor too big. It has the deep green, needle-like leaves characteristic of this species and grows to about 7 feet high and 8 feet wide in twenty years. This very dark-foliaged conifer is easy to grow and combines well with plants having larger or variegated leaves.
Japanese cedars thrive in full or part sun in well-drained, humus-rich, acidic soil and average moisture. May grow quickly when it first comes home from the nursery, due to the added fertilizer it gets there, but within a year it will settle into its dense, compact habit of growth.
Cryptomeria japonica 'Black Dragon' is an evergreen, coniferous shrub. It grows wider than high, with an overall pyramidal shape. In 20 years it will reach only 7 feet high and about 8 feet wide.
Hardiness: USDA zones 6 to 9

Season All Season
Date 2007-06-16
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Keywords: liverworts, Mosses, Lichens

PAL Question:

Both my front and back gardens have become covered in moss and/or liverwort. It has intermingled with groundcovers such as sweet woodruff and blue star creeper. I have dug up the liverwort in the past but it comes back. Any suggestions towards eradicating it would be greatly appreciated.

View Answer:

It would be important to distinguish among mosses, lichens, and liverworts. Mosses and lichens are not harmful to garden plants. One species of liverwort is known to be a bit of a pest, mainly in greenhouse-grown plants. A first step would be to bring samples to a Master Gardener Clinic for identification. See the following on moss and lichen in gardens:

There are researchers at Oregon State University who have done work on the species which is prevalent in greenhouses, Marchantia polymorpha, but the following information may not be relevant if that is not what you have growing in your garden. The first thing to do--if this is indeed the liverwort you are seeing--is to make sure you are not providing the ideal conditions for liverwort growth. Note that high nitrogen and phosphorus levels encourage growth: if you use fertilizer, check the levels of these nutrients. Avoid quick-release synthetic fertilizer. Below is information on methods of greenhouse (not garden) control of liverwort, from the OSU website:
"Before talking about how to kill liverworts, let's talk about conditions in which liverworts thrive. Liverworts grow vigorously in conditions with high humidity, high nutrient levels (especially nitrogen and phosphorus), and high soil moisture. In an environment that has any of these 3 conditions, it will be difficult to control liverworts (even when using herbicides). In order to effectively control this weed, you must make growing conditions for the liverworts as difficult as possible. To do this, you should attempt to create an environment where the ambient air is dry, the surface of the container is dry (as dry as possible), and nutrients are not available on the container surface."

The link above discusses postemergence control, but bear in mind that if something like acetic acid is used on liverwort growing on your plants it will affect the plants as well.

The Royal Horticultural Society says that liverwort will not harm plants (except by causing competition for small plants) but its presence indicates compacted, acidic, and/or bare soil.

The only time I have encountered liverwort is when transplanting nursery-purchased plants. With these, I physically remove the liverwort from the pot before planting into the garden. I wonder if your soil drains poorly, gets too much water, and/or too much fertilizer. I hope the information above will give you some ideas. Again, I recommend getting a conclusive identification before proceeding.

Season All Season
Date 2010-05-08
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Keywords: Fungal diseases of plants, Mushrooms, House plants

PAL Question:

I have a potted plant with a fungus growing in the soil. It is bright neon yellow and grows like a mushroom, but with no cap on top. The plant is in the basement near a window. The soil is damp and I've avoided watering for awhile to let it dry out. What do you think the growth is, how to get rid of it, and will it be harmful to my plant? I keep plucking them, but they grow back.

View Answer:

I have had questions about the yellow houseplant mushroom before, and I am guessing you are seeing the same thing. It is called Leucoprinus birnbaumii.

Michael Kuo's website, MushroomExpert.com has information about Leucoprinus. Excerpt:

"This little yellow mushroom and its close relatives are the subject of many frantic e-mails to MushroomExpert.Com, since it has a tendency to pop up unexpectedly in people's flower pots--even indoors! The brightness of its yellowness exhibits some rebelliousness, but it often creates a striking contrast to the green houseplants that surround it.

"Leucocoprinus birnbaumii won't hurt you, unless you eat it. It won't hurt your plant. It won't hurt your pets or your children, unless they eat it. There is no getting rid of it, short of replacing all the soil in your planter (and even then it might reappear). Since it makes such a beautiful addition to your household flora, I recommend learning to love it--and teaching your children to love it, too.

"You might also impart the idea that mushrooms are very, very cool--but shouldn't be eaten. Perhaps your child would like to become an awesome and famous mycologist some day. I would love to encourage your child's interest in mushrooms by putting his or her drawing of Leucocoprinus birnbaumii on this Web page (at least temporarily).

"Leucocoprinus birnbaumii is probably poisonous; do not eat it. Handling it, however, won't hurt you."

Season All Season
Date 2007-06-20
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Keywords: Tulipa, Narcissus, Iris, Bulbs

PAL Question:

This is my first year planting spring flowering bulbs, which grew nicely. I cut the dead flower and the stalk once it died back, and now the foliage is yellow. What am I supposed to do with the yellow foliage? Pull it out? Cut it off? Just leave it alone? Also, will planting some annual petunias now hurt the bulbs I have planted in the garden? How close can I plant the petunia to the bulbs? I was going to try and hide the yellow foliage.

View Answer:

The answer will depend on which bulbs you were growing. For example, daffodil stems should not be cut back until at least 6 weeks after the flowers have faded, and you should never tie the foliage in knots or braid it (this is a common but ill-advised habit). You can leave daffodils in the ground to naturalize and spread.

With tulips, you also need to wait at least 6 weeks from the fading of the flowers before cutting back the leaves.

With hyacinths, you can pull away dead foliage and flower stems as they fade. When the top growth has died down, you can either leave them in the ground or dig up the bulbs, dry them off, and store them for replanting.

If you are growing iris, you can cut the dead flower stems to the base, and cut away dead leaves in the summer. If they are bearded iris, the fan of leaves may be cut back in the fall to about 8 inches above the base.

(Source: The Plant Care Manual by Stefan Buczacki, Crown Publishers, 1993)

You can certainly plant your annual petunias quite close to bulbs like daffodils and tulips and other bulbous plants which are quite vertical. Just don't plant right on top of the bulbs. To disguise dying bulb foliage, use perennial ground cover plants that keep their leaves over the winter, and that have stems soft enough for bulbs to emerge through them. Hardy geraniums (true geraniums, also called cranesbill) and creeping veronica, such as Veronica peduncularis 'Georgia Blue,' are good choices. You can remove dried leaves as needed, and they can be tidied or groomed in early spring.

Season All Season
Date 2007-06-20
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Keywords: Magnolia grandiflora, Winter protection of plants

PAL Question:

We are looking into growing evergreen Magnolias as part of our nursery stock. Do you know what varieties will be the most cold hardy in the Pacific Northwest, and will be able to handle heavy snow the best?

View Answer:

You may have already come across this garden forum discussion on this very topic on GardenWeb.

Great Plant Picks suggests the variety 'Edith Bogue:'

"The slow growth and controlled size of 'Edith Bogue' make it a good choice for courtyard and patio plantings, and its branches have strong resistance to breaking in wet winter snows."

Their site also claims the variety 'Victoria' is resistant to damage from heavy snow.

This article from the Arnold Arboretum mentions Magnolia virginiana 'Milton,' also evergreen and supposedly resistant to breakage from snow loads because of its smaller leaves:

"The leaves are smaller in all dimensions than those of M. grandiflora, better suited to dealing with the snow loads that can be the death of the larger species, even for those cultivars that are otherwise quite hardy."

I looked at several of our books on Magnolias, but snow load doesn't appear to be a consideration for the authors--perhaps they've never walked around the Pacific Northwest after a snowstorm, and seen all the sorry-looking evergreen Magnolias bent and broken in the parking strip gardens! I suspect that even the snow-load damage-resistant varieties are susceptible to a degree. I've been observing the ones in my neighborhood. Those with a more upright, narrow structure seem to fare just a little bit better (gravity may make some of the snow fall off the foliage?) than the really wide-branching ones.

Season All Season
Date 2012-02-04
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Keywords: Fungal diseases of plants, Insect pests, Lonicera

PAL Question:

I noticed my honeysuckle, which is intertwined to look like a topiary bush with the greens and flower all bunched up at the top, to have yellowing of the leaves and drop off. Why are the leaves yellowing? It smells lovely and is green on the outside, but if you look under the canopy you can see many yellow leaves. Is it a disease? Should I use a fungicide?

View Answer:

There are a few possibilities. It might be a kind of leaf blight, as described by Iowa State University Extension.

Leaf blight is a fungal problem, but the control methods described above are not nontoxic, so you may want to look for a safer fungicide (example here), and also try to prevent the ideal conditions for fungus. Avoid wetting the leaves of the plant, and make sure there is good air circulation around the plant (by siting it properly, and by pruning to keep the plant's shape open).

Yellowed leaves could also be caused by scale, which is an insect. Do you see small bumps on the leaves and stems? If so, here are recommendations from The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale, 1996):

"Minor infestations can be controlled by scraping the insects off the plant with your fingernail, and by pruning out the most infested parts of the plant. You can also use a soft brush and soapy water to scrub scales off the stems, or you can apply dormant oil to the trunk and stems of the plant just before growth begins next spring, and use superior oil during the growing season."

Because I'm not certain which type of problem your honeysuckle may have, you should bring a sample to a Master Gardener Clinic.

Season All Season
Date 2008-02-07
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Keywords: Dendrobium, Orchidaceae (Orchid family)

PAL Question:

I just got a Dendrobium, it is Dendrobium eima x impact. The flowers are pink and white. I was wondering how I can tell if it is a deciduous one or an evergreen one. I still have months before winter, but want to make sure I give it the rest it needs when the winter does get here.

View Answer:

There are deciduous and evergreen types of Dendrobium. Unfortunately, I could not find information about the variety you are growing. If yours has soft canes, it is deciduous; hard canes are characteristic of the evergreen type. Here is information from Orchids Made Easy:
"Dendrobiums are separated into two main groups: hard-caned and soft-caned. Hard-caned Dendrobiums have tall pseudobulbs that are very thin and their leaves are generally a little darker in color than the soft-caned. Hard-caned Dens are evergreen and often keep their leaves for many years before they drop them. Hard-caned Dens grow spikes from the top of the cane and produce gorgeous flower sprays.

"Soft-caned Dendrobiums have leafy pseudobulbs that are long and slim. Their leaves are generally a little lighter in color than the hard-caned Dens. They grow leaves along the length of the cane and the blooms sprout from the individual stems that are along the cane itself. Soft-caned dendrobiums are deciduous and drop their leaves when the weather gets cold."

The American Orchid Society has a guide to growing evergreen Dendrobium for beginners.

There is also good general information on caring for orchids in the Brooklyn Botanic Garden guides on the subject. Generally, winter is the time to hold back on watering a bit, but also be careful about the plant's need for humidity--our heated homes in winter can be exceedingly dry. According to Orchids by Joyce Stewart (Timber Press, 2000), most orchids prefer 65-75% humidity during the day. She recommends "damping down last thing at night" during the winter (using a spray bottle or mister), if you have heat on in your house overnight.

Season All Season
Date 2007-06-20
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Keywords: Beans--Diseases and pests

PAL Question:

I have planted green beans three times because I have an annual problem of the leaves either being completely chopped off or they appear lacy and nearly gone. I have seen slug slime, so that may be some of the problem, but what does the lacy leaf indicate? I also have a lot of "potato bugs" or "sow bugs," could that be the problem?

View Answer:

According to The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale, 1996), lacy leaves on your bean plants might be the work of Mexican bean beetles. Parasitic wasps (Pediobius foveolatus) can be used to control the Mexican bean beetle. As a last resort, you can spray or dust your plants with pyrethrin. See links here:

From the Connecticut Agricultural Experiment Station

From the University of California

Large holes in the leaves may be caused by other beetles as well, such as the cucumber beetle, which can be managed by protecting your plants with row cover like Reemay. If damage is severe, you can use pyrethrin or neem spray.

Small holes in the leaves may be the work of flea beetles, and the management is the same as above.

The chopping off at ground level sounds like it could be the slugs eating shoots as they emerge, or climbing up the plant and eating it down to the ground. It could also be the result of cutworms. Look for these at dusk, and look during the day at or just below the soil surface. I manage these pests by looking for them frequently, and squishing them or cutting them in half with my pruning shears.

I had never heard of sow or pill or potato bugs (isopods) being a vegetable pest, but apparently they do have that potential if the population is large enough. See the discussion among gardeners on Gardenweb.

You might try fooling the pests by planting your beans in a different location, especially a raised bed.

Season All Season
Date 2007-06-20
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Keywords: Trees--Wounds and injuries, Thuja plicata

PAL Question:

I have a mature Western red cedar with an inverted-V gap in the bark, right at ground level. The point of the V is about 2 ft. off the ground; the base of the gap is perhaps 9-10" across. What's the current thinking on protecting this exposed area from diseases and critters? Paint with some sort of goop? Leave it alone? Or something else?

View Answer:

Here is a link to information on managing bark injuries, from Cornell University's Plant Disease Diagnostic Clinic, which includes illustrations. Excerpt:

"When a split occurs on a tree, what should you do? In recent years, quite a bit of research has been done on closure of tree wounds. These investigations have indicated that tree wound paints are of little value in helping a tree to callus over. For this reason, do not paint or try to seal a split with paint or tar. Tracing the bark around the split can be very helpful in aiding wound healing (Fig. 2). With a sharp knife, starting from one end of the split, trace around one side of the wound, about 1/2 to 1 inch back from the split bark. Stop at the other end and do the same procedure on the opposite side of the split. Knives should be sterilized between cuts by dipping them for several minutes in a 1:10 bleach:water solution or a 70% alcohol solution to avoid contaminating the cuts. Carefully remove the bark from inside the traced area. You should now have a bare area resembling the diagram in Fig. 2. Remember to leave this untreated. A tree growing with good vigor usually calluses over quickest. Encourage vigor in the tree with yearly spring fertilizer applications -- and be sure to provide adequate irrigation in hot, dry weather. Bark splits will often close over completely leaving a slight ridge in the trunk where callus tissue has been produced."

The book Practical Tree Management: An Arborist's Handbook by T. Lawrence et al. (Inkata Press, 1993) confirms the method described above. Trim back the bark to healthy tissue around the wound using tools such as a chisel, gouge, hammer, and sharp knife. Wound margins should be rounded, and damaged wood within the wound should be smoothed with a chisel or gouge, but only to the most minimal level (don't go deep).

If in doubt, I would recommend contacting a certified arborist for assistance. You can obtain a referral from Plant Amnesty or the Pacific Northwest chapter of the International Society of Arboriculture.

Season All Season
Date 2007-06-22
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Keywords: Micropropagation, Acer palmatum

PAL Question:

Do you have any information about micropropagation of the Japanese maple?

View Answer:

I found a series of replies to a question like yours on the University of British Columbia Botanical Garden's online forum.

An article formerly available online from the Oregon Association of Nurseries states the following:

"Keeping up with the demand for 'newness' means learning about and trialing different propagation techniques. That's where tissue culture, or 'in vitro micropropagation,' has been used as one propagation tool of many in the tool chest, said Gayle Suttle of Microplant Nurseries Inc. in Gervais, Ore. The company focuses on shade trees and shrubs. "No technique will dominate," Suttle said. 'What's going to work for the industry is, number one, focusing on quality and, number two, efficiency. If you sacrifice quality for cost, then you lose.'

"Micropropagation helps many nurseries get a jump-start on production of new items, improve the reliability of plant performance and start with clean stock. In the area of woody plants, micropropagation has had a particular impact on the nursery industry, allowing growers to cut the time needed to establish mother blocks and meet production demand, Suttle said. Also, there are some plants where branching is hard to come by, and micropropagated plants tend to branch more. 'If you can grow a plant by seed, there's nothing that beats throwing a seed into the ground,' she said.

"But there are plants for which normal propagation has problems -- the seed source is unreliable or unavailable, a graft is incompatible with its scion, budding problems arise in the field or roots fail to form on cuttings. Micropropagation fits as one way to keep growers successful and efficient.

"'Twenty-five years ago, there was a fear that micropropagation was going to take over the world,' Suttle said. 'That's never been a concept that's panned out. The industry is such a variable industry, with different people doing things differently. The goal is to be successful. You can save all kinds of money, but if you have a rotten plant, no one's going to buy it. Customers may buy a cheap plant one year, but if the quality is not behind it, they won't be back next year. They'll be looking for something else.'

"It was plant health and survivability that drove Dieringer Nursery Company toward organic growing practices nearly 13 years ago, and those goals keep the nursery from fully jumping into use of tissue culture. The company grows rhododendrons, relying mostly on vegetative propagation with a small smattering of grafting and an even smaller sample of plants produced via micropropagation.

"'Every couple of years we will bring in some tissue culture to evaluate the plant under our growing procedures, we'll get a new variety and it comes in by tissue culture,' said Jeff Dieringer, president of the Hubbard, Ore.-based company.

"The advantages of propagation by cuttings over other methods are exact replication of desired genetic characteristics and the more rapid time frame to finished product compared with starting from seed. Nearly all of the hundreds of thousands of rhododendrons Dieringer nursery handles in a year are grown using vegetative propagation, while maybe only a couple hundred are started from in vitro micropropagation.

"'It's a way to introduce a plant, but we don't get tissue culture starts and turn them into production plants,' Dieringer said. 'We watch that plant, its habits under our growing condition for three to four years to see if it exhibits normal growth. We do vegetative cuttings then, if they don't exhibit any juveniles.'"

The Miller Library has several titles on micropropagation in general, but I did not find anything specifically addressing use of this method with Acer palmatum. A good general text with several chapters on in vitro culture is A Color Atlas of Plant Propagation and Conservation by Bryan G. Bowes (New York Botanical Garden Press, 1999).

Season All Season
Date 2007-06-23
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Keywords: Bergenia

PAL Question:

I am trying to find out the difference between Bergenia Winterglut, elephant ears, and Bergemia pig squeak. The landscape plan I am following calls for the pig squeak, but I could only find elephant ears. Is Winterglut something special?

View Answer:

I think that the confusion arises from the fact that 'pig squeak' is a common name for Bergenia, as is 'elephant ears,' while 'Winterglut' is part of a cultivar name (Bergenia cordifolia 'Winterglut'). Bergemia with an "m" in the middle is just a typographical error. 'Winterglut' is also known as 'Winter Glow.' See the excerpt from Greer Gardens Nursery catalog below:

BERGENIA - PIG SQUEAK - (-40 F, USDA Zones 3-8) Bergenia are tolerant of a wide variety of conditions but soil that is too rich can cause soft foliage. Providing the plant with poorer soil conditions and some exposure, you will enhance the winter color. This plant prefers some shade, but will thrive in full sun if soil is deep and moist enough. Not for south Florida or the Gulf Coast.

30047 'Bressingham Ruby' - The mound of rounded, deep green leaves are up to 8" long. The foliage is maroon on the underside, and will turn beet red in the winter. In the spring, flowers of a very intense red are borne on nodding cymes. Will get 1' tall.

30965 'Bressingham White' - Has large, dark green foliage which is adorned by blooms that start out light pink and then fade to a pure white. They reach 12-15'' in height and blooms appear in the spring.

31673 ciliata - (-20 F, USDA Zones 5-8) Large (12'') fuzzy, rounded leaves and white flowers in early spring make this deciduous Chinese species a standout. Part shade and moisture retentive soil. Low growing to 10''.

cordifolia - (-30 F, USDA Zones 4-8)

31562 'Eroica' - Dark purple flowers in early spring. Foliage changes from light green to deep copper in fall, then a brownish red after first frost.

31035 'Winter Glow' - Deep reddish pink flowers bloom in spring, held above evergreen leaves. In the winter the leaves turn deep red. Will be 1' in height.

From Thimble Farms in British Columbia:

Bergenia `Winterglut' Ht.45cm. Z2. Thick clusters of florescent red flowers and dark green foliage . Fantastic red fall highlights

You may find this information from the website of a Seattle area gardener, Paghat's Garden, and this additional page, of interest. Excerpt:

"A good plant nearly impossible to kill is Bergenia, named for the 18th Century German botanist Karl August von Bergen. It is called Elephant Ears because it has giant round or heart-shaped leaves. My grandparents called Bergenias the Elephant Plant, because if an elephant stomped on it, it wouldn't die. But I notice the Sunset Guide only calls it by its scientific name, giving it no common name at all, so Elephant Ears may be somewhat a regional name, & Elephant Plant just the name our family used without authority.

"We get good red winter colors on our B. cordifolia 'Winterglut' & B. cordifolia 'Abendglocken.' The first photo at the top of this page shows both of these when they were first stuck into the hillside as tiny starts. In that early-April 2002 photo, the 'Abendglocken' on the left has already turned from red back to green & is starting to bloom, showing a glint of color in its buds. But 'Winterglut' on the right still shows a chocolaty-colored leaf, which began to green shortly after photographed."

Season All Season
Date 2007-07-02
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Keywords: Plant diseases, Holly

PAL Question:

I purchased a gallon size Japanese Holly (Ilex crenata 'Sky Sentry') 5 years ago and put it in a 12" diameter container. It has not grown much, and has been looking bad lately, so I thought it was probably root bound. To my surprise, when I took it out, there were no new roots--the root ball was about 3" deep and 6" across. Is this a normal root for the Ilex? What does it need to thrive?

View Answer:

Since you mention that the plant is not looking healthy, I wonder if it may have root rot.

According to North Carolina Cooperative Extension, Ilex crenata is highly susceptible to this fungal problem.

It is possible that there are nematodes feeding on the roots and diminishing the plant's ability to get water and nutrients from the soil.

Another North Carolina Cooperative Extension site provides descriptions of several problems affecting hollies.

The Organic Gardener's Handbook of Natural Insect & Disease Control by Barbara Ellis (Rodale, 1996) says that Ilex roots grow close to the surface, so perhaps the size of the root ball is not abnormal.

Missouri Botanical Garden has general information on this plant.

To determine what exactly is causing the plant's ill health, you may want to bring pictures and samples of the affected parts of the Ilex to a Master Gardener Clinic.

Season All Season
Date 2007-06-27
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Keywords: Nicotiana, Poisonous plants

PAL Question:

Can I grow flowering tobacco varieties, such as Nicotiana sylvestris, and harvest the leaves for smoking?

View Answer:

Nicotiana species are in the Family Solanaceae. Nicotiana sylvestris is a parent of cultivated tobacco, N. tabacum. You can surmise that the cultivated tobacco plant was bred for characteristics that the ornamental plants were not—that is, use of the leaves for smoking without (immediate, anyway!) dire toxic consequences. All Nicotiana species have toxic properties, but levels of those substances may vary from species to species, so it would be unwise to assume that leaves from the other varieties are 'safe' to smoke. For example Nicotiana glauca, a weedy species also called tree tobacco, does not contain nicotine but instead anabasine, which is extremely toxic to humans and animals, according to this weed report from Weed Control in Natural Areas in the Western United States.

According to The North American Guide to Common Poisonous Plants and Mushrooms (Nancy J. Turner and Patrick von Aderkas, Timber Press 2009), "all tobaccos should be considered poisonous to consume (smoking brings its own risks); some have caused fatalities. […] Poisoning through intentional or accidental misuse of nicotine and products containing it is a relatively common occurrence. Related species may contain other toxic alkaloids, chemically similar to nicotine." For this reason, we suggest that you enjoy Nicotiana sylvestris, N. alata, and other ornamental species for their flowers only. Also avoid growing Nicotiana near plants like tomatoes and others in the Solanaceae which are susceptible to tobacco mosaic virus (in fact, don't touch those plants after handling Nicotiana, or smoking tobacco products).

Season All Season
Date 2016-02-27
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Keywords: Bacterial diseases of plants, Syringa

PAL Question:

I have a 'Palibin' lilac that appears to have a bit of bacterial blight. I have pruned out the diseased branches. Is it too late to spray to control the disease? I didn't do a dormant spray this year, and haven't done any preventive spraying to this point, either. If it isn't too late, what spray product would you recommend? What else can I do to keep the blight under control?

View Answer:

There are cultural methods of dealing with bacterial blight you should try before using any spray. The information below should help.

Washington State University Extension's HortSense website recommends:

  • Avoid injuring plants to reduce possibility of infection.
  • Avoid overhead irrigation.
  • Maintain proper plant nutrition. Healthy plants resist disease better.
  • Plant disease-resistant species such as Syringa perkinensis, S. microphylla, or S. vulgaris vars. 'Alphonse Lavallec', 'Crepuscule', 'Floreal', 'Guinevere', 'Jeanne d'Art', 'Lutece', 'Maud Notcutt', 'Mrs. W.W. Marshall', 'Rutilant', or 'William Robinson'.
  • Prune and destroy infected tissues as soon as they are noticed.
  • Space plants properly and prune to provide good air circulation. This will slow down spread of the disease.

Here is more information from University of California, Davis's Integrated Pest Management site. Excerpt:

"Bacterial blight is promoted by prolonged rainy springs. Symptoms may be more extensive in wetter areas. Prune branches showing dieback and severe blight. Space plants to provide good air circulation. Prune during the dry season when infection is less likely to occur. Do not wet foliage with overhead irrigation; do not overfertilize. Small plants can be protected to some degree by keeping them covered by plastic (or moved under plastic). Plant resistant species if available. If the disease is systemic or cankers appear on the trunk, the tree will probably die and should be removed. If the disease is confined to leaves, damage is not usually serious and trees normally recover. Sprays do not give reliable control."

Season Spring
Date 2007-06-27
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Keywords: Anemone

PAL Question:

Do you have any suggestions for controlling the spread of some too happy Japanese Anemones? I know they spread by underground roots but do they also spread via seeds? If I put down a barrier how deep should it go?

View Answer:

I have also experienced this in my garden, and it is not difficult to dig up Japanese anemones and either compost them or offer them to fellow gardeners (with a warning!). Anemone x hybrida spreads easily by roots but can be propagated from seed. It is most likely that the spreading of the plant in your garden is mainly rhizomatous (by roots). If you don't want to dig up the occasional clump, you could try getting rid of the plant in areas where you do not want it, and then putting barriers such as plastic edging around the clumps you want to keep, although I think this requires at least as much labor as removing any unwanted anemones. Also, cut off spent flower stalks if you want to avoid seeds. However, the seedheads are flossy and ornamental in winter.

Here is general information on this plant, from Cornell University.

Here is information from University of Minnesota Sustainable Urban Landscape Information Series about edging material (use the search box in the upper right corner and search for 'edging'). This may give you some ideas on ways of containing the spread of the roots.

Season All Season
Date 2007-06-28
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Keywords: Fragaria, Cutworms, Fruit--Diseases and pests

PAL Question:

My small patch of strawberry plants has this year suffered from green fruit dropping off, forming neat piles under each plant. Each fallen fruit has a short bit of stem still attached. A few fruit are still attached. No sign of slug or squirrel damage, no signs of fungus of insect attack. The weather has been colder and wetter than average. Owing to natural layering, the plants are closer together than when first planted. This happened a couple of years ago, but we had a good crop last year. Any idea what's going wrong?

View Answer:

I wonder if this might be the work of cutworms. You can take a close look just under the soil surface, along the stems, and inside curled or folded leaves during the day, or take a flashlight at night, which is when they feed, and see if that may be why your strawberries are being cut away from the plant. If you find them, cut them with garden pruners.

Washington State University's pest and disease site does list the cutworm as a known pest of strawberries. Excerpt:

"Cutworms and armyworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The greenish, grayish, or tan caterpillars are hairless, nocturnal, and generally spotted, striped, or otherwise marked. They may be 1/4" to 1" in length and tend to curl up when disturbed. They may climb into the plant and feed on foliage, buds, flowers, or fruit. Armyworm behavior is similar to that of cutworms, but armyworms feed in large groups instead of individually. They tend to be voracious feeders. The caterpillars typically spend the day just beneath the soil surface or under debris near the host. Weeds are a primary food source for both cutworms and armyworms."

I looked at Pests of the Garden and Small Farm by Mary Louise Flint (University of California, 1990), but could not find any strawberry disease resembling what you have observed in your garden, which leads me to believe it is a pest problem. Here is a link to U.C. Davis's Integrated Pest Management page on strawberries.

Season All Season
Date 2007-06-28
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Keywords: Hedera helix, Invasive plants--Control

PAL Question:

In trying to eradicate English Ivy I am considering using Clorox on the roots. I have cut off all of the leaves. Is this safe and do I need to guard against nearby roots from trees that I want to save? If the Clorox will work I am assuming that I would use it undiluted for maximum effect. Any other ideas on English Ivy eradication?

View Answer:

Ivy is a tough plant to eradicate, as I imagine you already know. The resources I have consulted indicate that manual removal methods are more effective than chemical methods. Ivy apparently has an excellent defense system against chemicals. I could find nothing in the literature that suggested using bleach to kill the roots of Hedera helix (English ivy).

Here are links which may be of use to you.

From King County Noxious Weed Control.

From Portland, Oregon's No Ivy League.

Local garden writer Ann Lovejoy's article in the Seattle Post-Intelligencer. Excerpt:

"Why not just poison it? Using herbicide on ivy is both futile and dangerous. Ivy's waxy foliage repels herbicides, which run off to damage nearby plants and pollute water systems.

"To safely and steadily get rid of ivy, begin by cutting all vines that have scrambled up trees or posts. Remove as much as you can reach from each trunk. If you miss a few stubborn scraps here and there, don't worry about it. Just be sure that none of the vines remain uncut or are left dangling.

"Now remove all ivy at ground level by pulling strands and prying roots with a small hand-mattock or hori-hori (Japanese farmers' knife). Even if you miss a few roots (as you will), they won't all sprout back.

"Finally, mulch with a combination of woodchips and compost if you plan to replant soon. If you just want to keep the ground clear for a while, use coarse wood chips for mulch.

"To keep the mulched area clear, check it two or three times a year. You can quickly remove any new shoots that appear, along with as much root as possible."

Season All Season
Date 2007-06-29
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Keywords: Frost

PAL Question:

This winter, I was walking past a neighbor's garden and noticed a few dried stalks (not sure what the plant was) that were sprouting a candy floss-like substance. When I got down close, I could see it was ice coming out of cracks in the stems. What causes this phenomenon? Does it happen to only certain types of plants?

View Answer:

You were fortunate enough to witness an example of frost flowers, also called ice flowers, or crystallofolia, a term coined by Bob Harms (University of Texas, Austin) to distinguish the phenomenon from "frost flowers" which are sea ice. Not all plants exhibit these fanciful formations of ice crystals, but sometimes their common names will hint at this potential. Verbesina virginica, native to most of the central and southern reaches of the eastern United States, is known by the names frostweed and white crownbeard; Helianthemum canadense is sometimes called rock frost or frostwort. This is not a widespread occurrence, and there is no clear pattern dictating which plant families or genera are likely to produce these ribbon-like excrescences. A few others which do this include American dittany (Cunila origanoides), Isodon excisa and I. rubescens.

In a column (from December 18, 2013) called The Buzz, Memphis Botanic Garden's website explains the formation of flowers as follows: "When the ground is warm enough for the plants' roots to still be active, but the air temperature drops below freezing […] juices from the plant are expelled through slits in the stems […] This may happen multiple times over the winter since our ground rarely freezes far down, but once the moisture is gone, so are the frost flowers." The theories and explanations of why certain plants do this are far more complex. It may have to do with the xylem rays which carry sap from the center to the periphery of the stems, according to James R. Carter of Illinois State University. Plants with prominent rays are more likely to have ice flowers, which may be using the xylem rays as a source of fluid.

If you would like to increase the odds of witnessing these fascinating ice formations again in your own garden, you could try growing some of the plants on Carter’s list (avoiding any which are invasive in our area!).

  • Anemone halleri
  • Ceratostigma willmottianum
  • Echinacea species
  • Eupatorium cannabinum
  • Helleborus argutifolius
  • Origanum vulgare
  • Plumbago auriculata
  • Salvia coccinea

To this list, I would add Monarda didyma, the only plant on which I have ever seen frost flowers in Seattle.

Should you wish to read more, and see additional illustrations, there is an article by James R. Carter entitled "Flowers and Ribbons of Ice" in American Scientist (September/October 2013 ). The website Kuriositas also has a page of photographs of "Frost Flowers: Nature's Exquisite Ice Extrusion."

Season Winter
Date 2015-09-01
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Keywords: Dracunculus

PAL Question:

I recently purchased a house that has a relative of the corpse plant in the yard. It is a perennial about 30" tall and has been in bloom since yesterday with a deep burgundy bloom that is about 10" long. It has delicate, deeply lobed leaves.

Any idea what it could be or how to care for it? I was considering transplanting it since it sits just below our dining room window, under the eave of the house. Stinky! I imagine it will only bloom for a short time. Could it be rare?

View Answer:

I am guessing that what you have is the voodoo lily, or Dracunculus vulgaris.

The website of a Pacific Northwest gardener, Paghat, has information about this plant with pictures for you to compare with the plant in your garden. Vanderbilt University also has images of this plant on its Bioimages page.

For contrast, here are images of corpse flower, Amorphophallus titanum.

According to The Royal Horticultural Society's A to Z Encyclopedia of Garden Plants edited by Christopher Brickell (DK Publishing, 1996) the plant you have is frost-hardy, and grows best in full sun but will tolerate partial shade. You can protect it with a winter mulch. Native to the Mediterranean, Madeira, and the Canary Islands, they grow well in open glades in sheltered woodland, or at the base of a sunny wall. From what I have heard from other gardeners (we receive several questions a year about this plant), they do spread over time. If you wish to increase their numbers, they can be propagated by separating offsets in fall or spring.

Season All Season
Date 2007-06-15
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Keywords: Lilium (Lily family), Bulbs

PAL Question:

How do you remove the dead flowers from a Asiatic lily? Do you go to the main stem and cut it there or do you just remove the flower and leave the pod?

View Answer:

Here is what University of Minnesota Extension advises:

"Deadhead flowers as they fade, by breaking them off carefully. That way, none of the plant's energy is 'wasted' on seed production. Do not remove stems or foliage, though. They'll continue to put energy into the bulb as long as they remain green. Remove old foliage in late fall or early spring by cutting down the dead stalks."

Season All Season
Date 2007-06-25
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Keywords: Propagation, Cyclamen

PAL Question:

I have a Cyclamen that blooms in the fall, so I think it would be C. hederifolium. Right now there is a clump of 1/2 in. diameter "seeds" attached to curly spirals. I'm wondering if I can harvest those seeds and give them to others. In the book I'm reading, they say it is propagated by corms, which I assume I would find if I dug them up. What should be done at "cleanup time," which seems to be about now, as there are only a few dried up leaves left, and all those "curls and pods." I've had it several years and have done nothing to it. It blooms beautifully in the fall each year with deep pink flowers. I do see tiny starts at various places in the yard, so some seeds have moved around.

View Answer:

Propagation by seed is the most commonly recommended method according to the following resources:
American Horticultural Society Plant Propagation: The Fully Illustrated Plant by Plant Manual of Practical Techniques by Alan Toogood, The Royal Horticultural Society A-Z Encyclopedia of Garden Plants by Christopher Brickell, The Complete Book of Plant Propagation by Jim Arbury, Richard Bird, Mike Honour, Clive Innes and Mike Salmon, The Plant Care Manual by Stefan Buczacki and Cyclamen; A Guide for Gardeners, Horticulturists and Botanists by Christopher Grey-Wilson. Apparently propagation from corms is technical and difficult. However, if you choose to give it a try, The title Cyclamen, mentioned above, does go into some detail about the process.

You can thank the ants for the tiny starts you are finding in your yard, they eat the "sweet and sticky mucilage" that covers the seed, they then leave the seed alone where it lies, ready to germinate on its own afterward. (Cyclamen) As for the clump of seeds you are finding on your plant, their dark brown color indicates they are ripe and ready for sowing. They require dark, cool temperatures for germination (43-54 F) for C. hederifolium. It is recommended that the seeds soak for a minimum of 10 hours (a small amount of gentle detergent can be added) and rinsed thoroughly. They can be sown at the end of summer and produce flowers in about 14 months. (The Royal Horticultural Society A-Z Encyclopedia of Garden Plants and American Horticultural Society Plant Propagation).

Unfortunately I couldn't find much information for your question regarding clean up. However, I would suggest that it would be perfectly acceptable to remove the dead leaves and seed pods, including the curly spirals that are attached to them. You can choose to sow the seeds or give them away to friends. As long as you don't disturb the exposed curled tubers that may be present at or near the surface of the soil, I think you'll plant will be fine. You may also want to consider adding additional plants that show their true colors in the summer when your Cyclamen is dormant. This would mask the appearance of your Cyclamen and perhaps dissolve any need for clean up.

Season All Season
Date 2007-07-05
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Keywords: Pests, Amaryllis

PAL Question:

My Amaryllis bulbs are infected with syrphid flies. I have dug them but don't know what to do with the bulbs. What can I do to save them?

View Answer:

Until receiving your question, I had always known of syrphid flies as beneficial insects in the garden, so I considered the possibility that the bulbs might be infested with bulb mites, or mealybugs, which are fairly common pests of Amaryllis. That being said, in my research to answer your question, I came across an article by Whatcom County Washington State University Extension agent Todd Murray which describes the Narcissus bulb fly, which is indeed a syrphid fly, and does sometimes infest Amaryllis bulbs. Excerpt:

Monitoring and Management: There are no pesticide recommendations available for these bulb flies. But that's O.K.; we have many alternatives that we can use to avoid mushy bulbs. You should be thinking about trying these practices if you have a problem with bulb flies.

  • In May, on sunny days look for large bumblebee-like flies hovering around your flowers. Bumblebees will have two pairs of wings while bulb flies will have one. Grab your handy insect net (you all have one, right???) and catch the critters before they can do too much egg laying. This sounds tedious, but is very effective for protecting small plantings of susceptible bulbs. Remember, each female fly can lay up to 100 eggs! Plus, if it is a nice sunny day, you should be outside admiring and tending your garden anyway.
  • Adult flies use visual cues and smell to locate your delicious bulbs. After you have enjoyed your flowers, cover the bulb bed with a floating row cover, like Reemay*. Another recommendation given suggests that you mow down the vegetative portions of your plant and gently cover the tops with soil. Female flies will be unable to locate the bulb. Once no new foliage is sprouting, remove and store the bulb through the off-season. If you do this, I do not know the impacts this will have on next year's flower. That vegetation produces the bulb's energy reserve that is needed for next year's growth. Regardless, the earlier you can pull your bulbs out, the better chance that you will avoid bulb flies.
  • Bulb flies are less active in open, windy areas. Plant your beds in exposed windy places, if your landscape provides this type of climate.
  • Avoid any damage to the bulbs when handling and planting. The lesser bulb fly prefers damaged goods to healthy bulbs. Establishment of maggots is much easier if there are already rot producing organisms in the bulb.
  • Plant your bulbs deep, if they can tolerate it. Bulbs planted 25cm (or about 10") deep in the soil will evade attack by adult flies. I am unaware if planting this deep is practical.
  • When the time comes to pull up the bulbs, check the basal plate of each bulb. When you purchase new bulbs, check the plate for any signs of squishiness and rot. If you find some rot there, do not plant them and discard the rotten bulbs.
  • Infested or suspicious bulbs can be cleaned of maggots by soaking bulbs in hot water (43-44 C) for at least 40 minutes. Care must be taken to not exceed this temperature, because you will damage the bulb. This is a great way to kill other pests of bulbs, too.
  • Finally, if the problem persists, the sure-fire way to avoid bulb flies is to buy your flowers at the store like all the non-gardeners and black-thumbers out there. If you don't plant it, they won't come. This option is the one that I'm going to take now.

In the event that there are other pests present on your bulbs, this information from University of Florida Extension may be of interest. Excerpt:

"Spider mites are tiny animals (1/50 inch or 0.5 mm long) that cause injury similar to that of sucking insects as they feed on the leaves of amaryllis during warm, dry periods. Bulb mites attack rotting bulbs and tunnel into healthy bulbs, transmitting organisms that produce bulb rot. Bulb mites are particularly damaging to bulbs of amaryllis. Mealybugs are soft-bodied insects covered with a white, waxy material. When mature, they vary from 1/50 to 1/3 inch (0.5 to 8.5 mm) in length. They damage plant foliage by sucking plant fluids and may invade stored bulbs. Some control can be obtained by frequent syringing with a hose."

In case you are curious, here is information on the beneficial properties of syrphid flies, from University of California, Davis Integrated Pest Management.

Season All Season
Date 2007-07-06
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Keywords: Salvia, Drought-tolerant plants

PAL Question:

I recently planted several purple Salvia plants that have completely faded from beautiful, bright purple to beige. It has been really hot and dry and I've been watering them in clay soil once to twice a day. Is it possible that I'm overwatering them? Or do they need even more water since they were just planted?

View Answer:

I'm not sure what type of Salvia you are growing, but it is possible you are overwatering them. The heavy clay soil combined with watering 1-2 times daily sounds like too much for a plant that is drought-tolerant once established. To learn more about growing ornamental salvias, see this University of California, Davis Arboretum Review, #44, Fall 2003 article, "Salvias for Every Garden" by Ellen Zagory.

I would suggest watering less often, but watering more deeply, and possibly mulching around the plants. Some xeriscaping resources suggest using gravel, and it is mentioned in this document from New Mexico State University Extension, "Landscape Water Conservation: Principles of Xeriscape" by Curtis Smith, with the caution that although "some plants native to very well drained soils grow better in gravel mulches [...] rock mulch becomes very hot in our climate and can injure or limit growth of some plants. Ultimately, the mulch should be shaded by landscape plants that will provide environmental cooling. Using gravel mulch alone as a landscape element may result in increased home cooling bills and require greater weed control efforts."

This article by Seattle-area garden writer Ann Lovejoy on drought-tolerant gardening may also be of interest.

Season All Season
Date 2007-07-09
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Keywords: Hedera, Invasive plants, Climbing plants

PAL Question:

My question is about ivy for growing up a brick wall. What would you recommend? How do Boston ivy and English ivy compare for this purpose? We live in New Jersey.

View Answer:

First of all, it is important to know that clinging plants, such as Boston ivy and English ivy have the potential to "damage old, soft mortar and strip off pebbledash". (Gardening with Climbers by Christopher Grey-Wilson and Victoria Matthews) It is also suggested that these vines have a "structurally sound surface and must be prevented from reaching under house eaves and roof tiles and into window casements." (The New Royal Horticultural Society Dictionary Manual of Climbers and Wall Plants edited by JK Burras and Mark Griffiths)

The New Jersey Invasive Species Strike Team has a factsheet on both English ivy (Hedera helix)and Boston ivy (Parthenocissus).

In addition to taking this information into consideration, it would also be important to identify the amount of sunlight and the extent to which the side of the house will be exposed to harsh winter winds and temperatures. Neither Boston nor English ivy is recommended for full sunlight. Boston ivy will give you more fall color and interest and will withstand cold winters. (Simon & Schuster's Guide to Climbing Plants by Enrico Banfi and Francesca Consolino)

If you want to consider an alternative vining plant, you might want to install a trellis. That way you will not have to rely solely on vines which cling to the brick. You could try Clematis or some the honeysuckle species that are native to the northeastern U.S. There are several listed in this article by William Cullina, "Alternatives to invasive or potentially invasive exotic species," from the New England Wildflower Society:

  • Lonicera ciliosa (Orange Honeysuckle)
  • Lonicera dioica (Limber Honeysuckle)
  • Lonicera flava (Yellow Honeysuckle)
  • Lonicera sempervirens (Trumpet Honeysuckle)

Season All Season
Date 2007-07-02
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Keywords: Ensete

PAL Question:

I have a small, red-leaved banana plant. I am going to give it to my daughter in Iowa. What is the best care she can give besides full sun and moisture? What kind of dirt is best for replanting it and what kind of fertilizer should I feed it?

View Answer:

You are correct that Ensete ventricosum (Red banana) needs moisture and sun to thrive. The information I found about this plant indicates that it is not too particular about type of soil, but it is definitely frost-tender. Does your daughter plan to overwinter the banana in a greenhouse or other sheltered spot? The Missouri Botanical Garden site linked below suggests applying fertilizer during the growing season, but does not mention a particular type of fertilizer. (See last link below for more anecdotal information on fertilizer.)

Missouri Botanical Garden has useful information on growing Ensete. Below is an excerpt.

Winter hardy to USDA Zones 10-11. In St. Louis, plants may be grown outdoors during the growing season (either directly in the ground or in containers), but must be brought indoors for overwintering or they will not survive. Plants are best grown in organically rich, medium moisture, well-drained soil in full sun. Plants tolerate and often appreciate some part shade or light filtered sun in the heat of the day. Plants need consistently moist soils that do not dry out. Fertilize plants regularly during growing season. Site plants in areas protected from strong winds which can severely damage the large leaves. For containers, use a well-drained potting soil mix. Keep container soils consistently moist but not wet. In St. Louis, outdoor plants must be overwintered indoors, either in a sunroom/greenhouse or by forcing plants into dormancy. Options for overwintering include:

  1. Bring container plant indoors in fall before first frost and place container in a large sunny room for overwintering as a houseplant, with reduced water and fertilization;
  2. If container plant is too large to bring inside as a houseplant, cut foliage back to 6-8" in fall after first frost, and store container in a cool, dark, frost-free corner of the basement until spring, with periodic addition of a touch of moisture as needed in winter to prevent the soils from totally drying out;
  3. If container plant is too heavy or too large to bring inside, remove plant from container in fall before first frost, wrap roots in plastic and store in a cool, dark, frost-free corner of the basement until spring (foliage may be trimmed back or left on the plant and allowed to brown up in the normal course);
  4. If growing plants directly in the ground, dig, wrap roots, trim back the leaves and store as in option #3 above. After flowering and fruiting, the pseudostem dies. Propagate by seed or tissue culture.

The Plants for a Future database also has information on growing this plant.

There is information on fertilizing on the site of the Northwest Palms forum. Excerpt:

I promised in a thread a while back that I would post the fertilizer I use for feeding my Ensete ventricosum maurelii. Here's what I typically do:

The plants get set out in mid May. They have been dormant in the unheated basement since November. When they were dug up they had all their leaves cut off except the central growing one. The root ball gets covered with plastic to help keep moisture in. Over the winter they have lost a lot of their water but are still succulent and ready to put on new growth (usually they are already growing before being set out). Their root ball was kept small to make storage easier and they were watered sparingly and kept just barely moist for their period of dormancy. Last year the biggest plant was over 300 pounds (without leaves!) when dug up, but it will have lost about a third of that weight by the time it is planted out.

We plant them into areas of the yard where the soil is 100% compost. They get put in planting holes that have about 6 cups of pelleted shake/feed fertilizer (24-8-16 or similar) mixed into the bottom of the planting hole as well as a good sprinkling of pelleted micronutrients, iron and magnesium. But that's just the start...

After planting, they are generously watered in with transplant fertilizer and top dressed with manure or SeaSoil or both. Then, I wait for full-on new growth to start. As soon as it does, the bananas get fertilized weekly. I use urea (46-0-0), super phosphate (0-45-0) and potassium (0-0-50) and make my own mix using a ratio of 2:1:1. I dissolve 1/2 cup urea with 1/4 cup phosphate and potassium in a small amount of hot water. This super concentrate gets diluted into 10 litres of water and each Ensete plant gets this shot of fertilizer, watered in, every week from early June to October. (As they get dug up for winter, I'm not too worried about late season applications of fertilizer.) Every few weeks they also get some magnesium and some fish fertilizer. There doesn't seem to be any way to burn them with fertilizer when planted in the ground. (I wouldn't use an aggressive fertilizer schedule like this for plants in pots.) Use caution as nearby plants can suffer from such high levels of fertilizer--good reason to surround your bananas with cannas and Colocasias etc.

The other bananas we have (basjoo, sikkimensis, Orinoco, zebrina, Musella, itinerans) get a similar schedule but smaller quantities of fertilizer as they just can't match the maurelii for the "volume" of the plant (the biggest basjoos get about half the amount).

As other people have also pointed out, the amount of water they get is also critical. They all love water but must still have good drainage (we plant ours in raised mounds).

So there's obviously no magic to anything I do--I just experimented with how much fertilizer they can take and haven't hit the limit yet.

My only caution is beware of the monster you are creating. Digging up several 300+ pound plants, moving them (in our case, down a flight of stairs into the basement), storing them and then reversing the procedure in the Spring is back-breaking work. Perhaps ours will get too big this year (this will be their 3rd summer) to do this. Last year they were 17 feet tall..."

Season All Season
Date 2007-07-09
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Keywords: Landscape irrigation, Microirrigation, Xeriscaping

PAL Question:

We are putting in a new garden, and want to install a drip irrigation system to conserve water. The area is full sun. Can you direct us to some information on systems, and offer suggestions on plants?

View Answer:

Here is some information from a colleague who has experience installing and maintaining watering systems on a large scale (at Seattle Public Library's sites).

Drip irrigation

  • a sprinkler system using broadcasting spray heads is difficult to install and wastes water; they also contribute to fungal diseases
  • these systems also have to be blown out in the fall (winterized)
  • drip irrigation is easy to install

Hints:

  • install after the plants are in, or place parallel lines appropriately spaced to provide enough water while allowing for plant root zone increase
  • if installed after plants are in, try to encircle the root zones of trees and shrubs, allowing for increase in size
  • no need to encircle perennials; they are fine with a line on one or both side
  • for such a large area, use more than one zone or there will be no pressure (and no drip) at the end of the line
  • use a pressure reducer at the water source or the lines may come apart at junctions
  • if on a slope, follow the contours of the slope
  • bury at least 6 inches so settling and soil loss do not expose lines--and so lines don't freeze (no winterizing)--but too deep and you can't tell if it's working or not
  • draw a picture of the system
  • anchor the line with stakes (they are the shape of croquet wickets, but ~ 4" x 2") and can usually be purchased with the drip line
  • buy "splicing" supplies for breaks: female connectors are easier to install and I think Netafim is the most versatile line
  • scheduling: staggering helps (a short watering period followed by a long one) and remember that it has to be left on for a long time (i.e., 1-2 hours for the long session but not every day)

The Saving Water Partnership offers the plant list and watering guides linked here:

The Plant List
Smart Watering Guide
Soaker Hoses

See their tips on the best practices for watering.

Here is an article on drip irrigation from Fine Gardening.

I think that the best plant choices for your site in full sun will be drought-tolerant perennials, shrubs, and trees. Here are links to resources on selecting plants and maintaining a low-water-use garden.

Colorado State University Extension features several links on Xeriscaping.

An article on drought-tolerant gardening by Ann Lovejoy.

An Agusut 2004 article by Valerie Easton in the Seattle Times on drought-tolerant garden design.

Here are links to a booklist and a page of resources from the Miller Library.

You may also want to make a practice of mulching the garden to conserve water. Excerpt from www.greenbuilder.com:

Use a deep layer of mulch in planting beds to help retain moisture, slow weed growth, and prevent erosion.

The use of mulches on sloped areas along with terracing and plantings can help prevent runoff and erosion problems.

Examples of organic mulch material include:

shredded bark
wood chips
pine needles
straw
pecan hulls
cotton seed hull
composted leaves
shredded cedar

The depth of mulch needed will depend on the type used. As a general rule, the coarser the material, the deeper it should be applied. A 3 to 4 inch layer of bark mulch should be sufficient. Mulch needs to be reapplied as it decomposes.

The book, Water-Wise Gardening by Thomas Christopher (Simon & Schuster, 1994), recommends matching the mulch to the planting. For example, using pine needles around a clump of evergreens enhances the woodland appearance of the landscape. Using organic materials (such as compost, bark, pine needles, leaves) as mulch moderates the access of air to the topsoil, and conserves humus. Mulch suppresses weeds and keeps the surface of the soil from crusting over. Ann Lovejoy's book, Organic Design School (Rodale Press, 2001), recommends compost as the ideal mulch. Finished compost can be pressed through a fine mesh screen to topdress ornamental plants, while coarser compost can be used around shrubs and trees. Compost is a feeding mulch, improving soil texture as well as nutritional value. Here is what Lovejoy has to say about wood by-products as mulch: "To a greater or lesser degree, most tie up soil nitrogen temporarily as they decompose (fresh sawdust uses the most nitrogen, while coarsely ground wood chips use the least. Although I never use shredded bark as mulch on planting beds, many gardeners do. It makes an attractive, deep brown mulch (that) does not tend to rob nitrogen from the soil." She cautions against using thick layers of pine needles (over 2 to 3 inches) which can get matted down and shed water instead of letting it reach plants' roots.

Here is information from the University of Georgia Cooperative Extension, describing the best choice of mulch for a drought-tolerant garden:

Generally, the best mulch for the landscape is one that is organic, fine-textured and non-matting. Examples include pine straw, pine bark mini-nuggets, shredded hardwood mulch or cypress mulch. Inorganic mulches, such as rock or gravel, are not good mulches because they absorb and re-radiate heat around the plant canopy and increase evaporative loss of water from the plant. Fine-textured mulches, such as mini-nuggets or shredded hardwood, do a better job of holding moisture in the soil than more porous coarse-textured mulches.

Season All Season
Date 2008-02-07
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Keywords: Acer palmatum dissectum, Grafting, Woody plant propagation

PAL Question:

I have some standard Japanese maples onto which I'm trying to T-bud the weeping laceleaf maple. I've had pretty limited success, so I wonder if there's something I'm doing wrong. I've tried at different times of the year: late spring, summer. I cut a young small branch off the weeping Japanese maple. The I cut off a leaf bud. I use a very thin slice under the bud, and cut the leaf off the stem. I cut the T about an inch long in the standard Japanese maple, and slide the bud in. I've used duct tape and plumbing tape. I don't cover the bud but try to snug right up to it with the tape. I only get about 5-10% success doing this. Any suggestions?

View Answer:

You may want to consult the American Horticultural Society Plant Propagation manual (edited by Alan Toogood; DK Publishing, 1999), as it has detailed (and illustrated) information on T-budding and chip-budding. In the description of T-budding, the book emphasizes the importance of not pushing too hard into the bud. It also says to "sever the remaining tail of the bud by cutting into the bark again at the horizontal cut. Then secure the bud in place with plastic tape or raffia in the same way as for a chip-budded ornamental tree, leaving the bud uncovered to avoid exerting too much pressure on it." Texas A & M University also has an illustrated explanation of T-budding.

According to J.D. Vertrees's book Japanese Maples (Timber Press,2009), chip-budding is advantageous because it can be done at almost any time of year and uses less material per graft, allowing growers to make more trees with less. In any case, as long as your grafting knife is nice and sharp and you're working carefully, don't worry that not every graft takes. Professional propagators sometimes make four grafts expecting only one to take. You may find this article from Auburn University about grafting a Japanese maple (by Ken Tilt) useful.

Season All Season
Date 2010-05-20
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Keywords: Alstroemeria, Poisonous plants, Edible flowers

PAL Question:

I am planning to decorate my wedding cake with Alstroemeria. Are these flowers safe to use? The flowers won't be eaten, but will be in contact with the icing.

View Answer:

The website of National Sustainable Agriculture Information Service has a page of resources on edible flowers, including links to information about toxic plants. Alstroemeria can cause contact dermatitis when handled, and ingesting the plant can cause gastrointestinal problems. See the following information on Alstroemeria from North Carolina State University Extension.

Rather than take any chances, I recommend restricting your decoration choices to edible flowers. A mixture of calendula, lavender, and violet blossoms, for example, might be an attractive option. North Carolina State University Extension also has an article on edible flowers.

Iowa State University Extension has useful guidelines on selecting edible flowers.

Season All Season
Date 2007-07-18
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Keywords: Sheet mulching, Yucca

PAL Question:

Our home in Seattle came with a large number of established Yucca plants, and we would like to get rid of them. However, they are quite stubborn. We've tried a few things, including digging them up, but the root system seems quite deep and extensive and they always come back, and quickly! Any suggestions? I've thought they were non-native, but I guess they could be the sort that are found in eastern WA. Are there invasive species here in western Washington?

View Answer:

As you have observed, Yucca is very difficult to eradicate completely. Most of the literature on the subject suggests using herbicide, but even this may be ineffective, which makes the risk of using harmful chemicals to control the plant seem even less worthwhile. There are quite a few informal discussions on how to get rid of this plant on various online gardening forums, and one mentions local gardening expert Ciscoe Morris's method for getting rid of unwanted Yucca:

"...he cut it back to ground level and put a couple of squares of heavy cardboard over it, piled on some compost/bark to hide the cardboard. I'm not growing yucca, but he said it really worked for killing it without breaking your back. Leave in place for a year."

The technique described here is called sheet mulching. This involves laying down overlapping layers of cardboard and then covering thickly with leaves, compost, and other materials. Agroforestry.net offers information on how to do this. StopWaste.org provides additional helpful information.

Here is an excerpt from an answer to a question similar to yours, written by one of my colleagues here at the Miller Library:

"The general idea is you spread out a layer of cardboard or newspaper (about 4-6 sheets) and then cover that with a layer of organic mulch (compost, straw, alfalfa hay--available at feed stores, wood chips, coffee grounds, etc.). Then wait 6-8 months. This is not an exact science because there are many variables, such as thickness of newspaper, type of mulch and what type of plant you're trying to kill. Perennial weeds and especially coarse grass will push through the cardboard once it starts to break down so it is critical that if and when this happens you pull the mulch back and put down more newspaper/cardboard, and then replace the mulch."

Yucca is not (yet) considered invasive in our state. Here are links to information on locally noxious weeds.
Washington Noxious Weed Control Board.
King County's Noxious Weed Control Program.

Season All Season
Date 2007-07-11
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Keywords: Vegetative propagation, Nandina domestica

PAL Question:

I have a Nandina (heavenly plum blossom) that is getting really top heavy and I need to find out how to divide it or cut it back and root the cuttings. I've been reading up on it and there is very little information about propagating them.

View Answer:

The book American Horticultural Society Plant Propagation by Alan Toogood (1999) recommends taking nodal greenwood (similar to softwood) cuttings in the summer. The shrub can also be propagated by division but this is recommended in the early spring and not in summer due to the increased risk of wilting and scorching.

Rainy Side Gardeners in the Pacific Northwest notes that fresh seed (as soon as it is ripe) can be germinated in six to eight weeks. Old seed may take up to two years to germinate. Semi-ripe cuttings can be rooted in the summer.

As for pruning the Nandina, the American Horticultural Society Pruning and Training: A Fully Illustrated Plant-by-Plant Manual by Christopher Brickell and David Joyce (1996) suggests that plants can usually be renovated by cutting back old canes to ground level in the early spring when the older leaves have turned from red to green. Rainy Side Gardeners suggest cutting the oldest canes down to the ground, discouraging the shrub from getting top heavy and falling over. The pruning will keep it growing a denser growth lower down on the shrub.

A Practical Guide to Pruning: How and When to Prune for Better Shrubs, Trees, Fruits and Climbers by Peter McHoy (1993) suggests cutting one out of every three canes to the ground. His recommendation is not to do this each year.

Paghat's Garden (a website maintained by a local gardener) had this to say:

"Nandina thrives in considerable shade, but has a tendency to become leafless underneath unless it can get sunlight around the lower part of the plant. Before I transplanted this one, it was in a lot of shade, & needed to be staked because it became top-heavy. This did not necessarily harm its looks, because the species' tendency to lose leaves at the bottom gives it the appearance of a miniature tree with long trunk, & I used the "empty" space around its base for small ferns. But when transplanted to a sunnier garden, it became more broadly bushy & the trunk became stronger, no longer needing to be staked."

Season All Season
Date 2007-07-16
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Keywords: Washington Park Arboretum, Fothergilla, Polystichum, Hamamelis mollis, Kalmia, Actinidia

PAL Question:

I'm thinking of planting the following plants in my garden but would like to see them first. Can you tell me if they are at the Washington Park Arboretum? The plants are: Chinese Witchhazel, Witch Alder, Mountain Laurel, Soft Shield Fern, and Variegated Kiwi Vine.

View Answer:

The Washington Park Arboretum has many examples of Hamamelis mollis, or Chinese witch hazel (unless you meant Corylopsis sinensis or Loropetalum chinense, which also go by the common name 'Chinese witch hazel'). Kalmia latifolia (Mountain laurel) and Fothergilla (but not Fothergilla gardenii, which is Witch alder) are also in the Arboretum. The variegated kiwi, Actinidia kolomikta, used to be grown here at the Center for Urban Horticulture. Soft shield fern, or Polystichum setiferum, may be in the Arboretum, but is not listed, as it is not a woody plant. You can search the Washington Park Arboretum's Living Collections database by the plants' scientific or common names (sometimes it's best to search the scientific name, for clarity). You can search the Arboretum's interactive map and there is also a trail map linked here which provides information on large collections of plants, so you can get a sense of where to find things. You can go to the Graham Visitors Center in the Arboretum and ask for assistance in locating the witch hazels (some are in the Witt Winter Garden, and others are in a grove on the south end of the park) and other plants.

All of these plants grow well in our area. I have a dwarf form of Fothergilla in my garden, and it has been thriving. I have also seen many of the other plants in your list growing happily in private gardens in Seattle. Since you wish to know what they look like, here are several links to additional information with pictures.

Hamamelis mollis picture >

Fothergilla gardenii Picture 1
Picture 2

Kalmia latifolia Picture 1
Picture 2

Actinidia kolomikta Picture 1
Picture 2

Polystichum setiferum Picture 1 (from a local gardener)
Picture 2

Season All Season
Date 2007-07-12
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Keywords: Guizotia abyssinica, Seeds, Ethnobotany

PAL Question:

I bought some shiny dark seeds at an Ethiopian grocery store. The proprietor said they were good for sore throat. The name of the seed sounded something like 'nuk.' Can you tell me what plant they are from? And is it safe to use them?

View Answer:

By guessing at different possible spellings, I came across a plant whose Amharic name sounds like 'nuk' or 'noug.' I also showed your sample seeds to an Eritrean colleague, and confirmed that they were familiar to him for their high oil content, but also for steeping in hot water to make a kind of tonic. I can't recommend consuming them medicinally; you would need to speak to a medical professional. But I can tell you that the plant source is Guizotia abyssinica. It is in the daisy family (Asteraceae), and has a yellow flower that might remind you a little of a yellow daisy. There is research being done at University of British Columbia's Botany department on this plant and its potential as a crop to increase food security and alleviate poverty in Sub-Saharan Africa.

Purdue University researchers are looking into cultivating this plant (also called Nigerseed) in the Midwestern United States.

Wikipedia has additional information about this plant.

Season All Season
Date 2014-08-06
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Keywords: Daphne

PAL Question:

I have a Daphne odora which had aphids on it early this spring and I kept hosing it with water and got rid of the aphids (didn't spray with any chemicals). Lost a lot of leaves but now has new growth. Problem now is all the leaves look wilted like it lacks water and doesn't seem to be growing. I have watered it real good during the hot weather but it doesn't seem to be working. The plant is about 7-8 years old and has done well until this year. It gets morning sun and afternoon shade. Am I watering too much or is it because of the heat?

View Answer:

Daphnes can be a bit fussy, and as this article by Sarah Raven on Daphnes from the British paper the Telegraph mentions:

"Daphnes like life pretty constant, not too wet and not too dry, so, particularly when they're settling in, give them a little regular watering if the rain doesn't do it for you. They need and like good drainage, so always add plenty of organic matter (and some grit if you garden on clay). And don't despair if your plants don't go on forever. Daphnes rarely last more than 15 years and you'll almost never see a shrub older than 20. Plan on taking cuttings after flowering every five years or so to make sure you always have a daphne or two in your garden."

Signs of winter damage are similar to signs of drought problems, so it can be confusing. The foliage can be scorched if the plant receives hot afternoon sun, but your plant is in afternoon shade. To add to the confusion, yellowed leaves which drop can be symptomatic of excess water AND excess drought, as well as a delayed reaction to a cold winter. My own Daphne odora has this same problem, and always loses some of its leaves, develops new growth, but grows slowly. This plant requires good drainage, so that is another consideration.

Here is local gardener Ed Hume on Daphne odora:

"It is important to note that this type of Daphne needs to planted in a spot where it gets protection from the hot mid-day sun. An eastern location or similar spot is ideal. In addition, this one is not quite as hardy as the others, and may need to be given some cover protection, should temperatures dip below 25 degrees. Frost or sun burn, will show-up in a blackening of the tips of the leaves and in severe cases the leaves are apt to drop from the plant. The dark green evergreen leaves often have a cream-colored margin along the outside edge."

Another local gardening expert, Ciscoe Morris, says the following:
"These plants will thrive in the right conditions, but you will be disappointed if you plant it in the wrong spot.Growing Conditions: Morning sun; organic, well-draining soil. Do not over-water in summer, especially in clay soil. Daphne odoras do best in morning sun and afternoon shade. Give it well-draining soil (amend with compost). During summer, water only as often as needed to keep it alive."

Based on all the variables, I suggest you water it less often, and check to make sure it has adequate drainage. This can be a challenging plant, so be patient and hope for the best.

Season All Season
Date 2007-07-18
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Keywords: Abies, Trees--Diseases and pests

PAL Question:

We planted a young Fraser fir last March. It has a lot of new growth, but has developed some dead-looking tips here and there that are a reddish rust color. I am wondering if we have a serious problem or should I just remove the affected tips and not worry about it? I have noticed a lot of trees this summer on my travels out through the Cumberland-Enumclaw area that look a similar cinnamon color and are totally dead!

View Answer:

The problem you describe could be the result of drought injury, or it could be one of several rust and fungal diseases which affect fir trees. Was the tree watered well after planting? Here is information on drought injury, from Oregon State University's plant disease database (no longer available online). Excerpt:

Drought injury usually progresses from the top of the tree downward and from the outside to the inside of the crown. Top dieback and branch death may be common. Defoliation of the mid-crown or loss of needles at the base and tip of shoots can also occur in Douglas-fir. Older needles commonly turn yellow and are shed prematurely. Roots may be alive even though the entire above-ground parts are dead. Winter injury, gopher and root weevil problems can produce similar symptoms.

Your description also sounds like the symptoms of Phytophthora, a fungal disease which is common in our area. Excerpt:

Phytophthora root rot is usually a problem only in areas with poor drainage or where flooding occurs. The fungus attacks the roots, which rot and die. The infection moves up into the crown, where the cambium (soft inner bark) turns reddish-brown or caramel in color instead of the normal white to greenish color. Older trees may develop cankers on the trunk, which are a dark reddish-brown when cut. The cankers may be accompanied by split bark and oozing pitch. Lower branches wilt, turn dark red, and die back. Younger trees are often killed outright, while infected mature trees may show wilting, branch dieback, and/or gradual decline.

Missouri Botanical Garden's Integrated Pest Management site has information and includes an image of Fraser fir suffering from Phytophthora.

The Connecticut Agricultural Experiment Station has published a guide entitled "Recognizing and Managing Phytophthora Root Rot and Other Conifer Diseases" which may be of use to you. (Caution: this is a large file!)

I recommend taking a sample of one of the cinnamon-colored branches to a Master Gardener Clinic, and also taking photos of the whole tree, so that you can have the problem diagnosed. If you are near Enumclaw, the Pierce County Master Gardeners offer diagnostic clinics.

Season All Season
Date 2007-07-25
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Keywords: salt-tolerant plants, Seaside gardening, Ornamental grasses

PAL Question:

What ornamental grasses can I plant near salt water, and is there a local nursery that specializes in grasses?

View Answer:

As far as nursery sources, I think a full-service nursery is your best bet for finding ornamental grasses. The only "specialist" in grasses I could find is Walla Walla Nursery, which seems a long way from Seattle to go.

King County's interactive native plant guide also includes a page on marine (salt water) shoreline plants. At the bottom of the page, note the three native grasses which are recommended:

  • Lyngbye's sedge (Carex lyngbyei)
  • tufted hairgrass (Deschampsia cespitosa
  • dunegrass (Elymus mollis)

The following list of plants according to their salt tolerance comes from University of Minnesota Extension, but there may be some ornamental grasses that will do well here.
From the lists:

  • Calamagrostis acutifolia 'Karl Foerster' (Karl Foerster reed grass): high tolerance
  • Schizachyrium scoparium (Little bluestem): high tolerance
  • Elymus arenarius (Blue Lyme grass): high tolerance
  • Pennisetum alopecuroides (Fountain Grass): high tolerance
  • Festuca 'Elijah Blue' 'Elijah Blue' fescue: moderate tolerance

In her book Gardening at the Shore (Timber Press, 2006), Frances Tenenbaum lists a number of ornamental grasses (in addition to dune grasses):

  • Festuca glauca
  • Miscanthus sinensis
  • Muhlenbergia capillaris
  • Stipa tenuissima [now renamed Nassella tenuissima--in my experience, this grass is aggressive, seeding itself everywhere; the seedheads stick to people and pets who walk past it]

There are many attractive cultivated varieties of some of the plants listed above, and most local nurseries will carry them.

Season All Season
Date 2010-05-27
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Keywords: Acer circinatum, Tree roots

PAL Question:

I moved into a house built in 2001 on a cement slab (slab height = 18"). Around 1 foot from my foundation is planted a Maple tree. I have been told that it is a Vine Maple. It is around 15 feet tall. My neighbor told me to pull out the tree because the roots will crack the foundation of my house. I don't want to get rid of the tree unless this is true. I went to a nursery today, and they said that it is very unlikely that the tree will damage the foundation (unless the foundation is already cracked and the roots make these cracks worse). What do you think? I have no idea if the foundation has cracks that the tree could exacerbate or if a Vine Maple in general would crack a foundation like this.

View Answer:

I do think that planting anything one foot or less from the house is not ideal, especially a tree. However, vine maple roots have a low potential to cause damage, according to the database of the Urban Forest Ecosystems Institute (see full tree record for Acer circinatum).

On the question of how close to a house a tree can be planted, I found the following from New Mexico State University Extension site, in answer to a question like yours about root damage potential:

"A more important consideration is keeping the branches from rubbing against the house and damaging the stucco, siding, or paint and shingles. By planting the plant a distance greater than the expected mature crown radius from the house, you will avoid damage to the house by branches. You will still benefit from shade if the tree is properly positioned.

"Many trees are planted so that their branches are trimmed to be higher than the roof and then grow over the roof. Remember, if one of these large branches breaks in a wind storm, it can damage the roof, so distance from the house is the best protection from such damage. Learn how widely the branches spread from the trunk when the tree is mature and plant at least that distance from the house. Yes, you can break this rule-of-thumb, but the hazards increase when you do."

You may want to consult a certified arborist to evaluate the situation, and see if you can keep the tree where it is. To find a certified arborist, contact Plant Amnesty or the Pacific Northwest Chapter of the International Society of Arboriculture.

Season All Season
Date 2007-07-25
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Keywords: Solanum tuberosum, Vegetable varieties, Vegetable gardening

PAL Question:

I would like to plant a second crop of potatoes in July. Could I use potatoes dug from my first crop this year or should I try to find seed potatoes?

View Answer:

You can plant mid-season and late potatoes this month, but there are particular varieties that are best suited to planting at this time. This is one reason not to plant the potatoes you just dug (which are an earlier variety).

Here are links to additional information:

From the University of Illinois Extension.

Growing Potatoes in the Home Garden from UC Santa Cruz.

Steve Solomon's Growing Vegetables West of the Cascades (Sasquatch Books, 2000) says that because of the large number of viruses which can affect potatoes, you should not carry over your seed (replant). It is safest to use certified virus-free planting seed. He says that your crop might be fine the first time you replant your own potatoes, but they will become increasingly susceptible to viruses.

Season Summer
Date 2007-07-18
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Keywords: Hydroponics

PAL Question:

We recently started a hydroponic garden and currently are starting lettuce, arugula and spinach from seed. The seedlings are getting along pretty well, in spite of a mid-July start. Over the past week or 10 days there is also a considerable amount of algae growing in the water. Will this hamper the growth of the desired crop? Should we attempt to control the algae growth, and if so, how? We look forward to your advice.

View Answer:

Algae growth is encouraged by light, so make sure your hydroponic reservoir container excludes light. Prevention is safer than treatment with algicide, which is not only phytotoxic, but not something you would want on edible crops.

Here are links which may be of interest:

Hydroponics as a Hobby, from University of Illinois at Urbana-Champaign Extension

Home Hydroponics from Virginia Cooperative Extension.

The information excerpted below comes from a now-defunct page from a home hydroponics website called Maximum Yield:

Other studies have found 'organic' algae control methods such as adding certain 'grapefruit seed extracts' to the nutrient will kill algae without harming the plants - this is a method used in drinking water, fish ponds, lakes etc and appears to work well. There could be the potential, in larger hydroponic tanks to use 'Barley straw rafts' as a means of algae control as has been proven to work in ponds, lakes and other water ways. However the best method of algae control will still always be prevention of the problem, so excluding light should be the main emphasis in systems with algae problems.

Season All Season
Date 2007-07-25
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Keywords: Verticillium, Tomatoes--Diseases and pests

PAL Question:

I was just outside checking on the slow ripening progress of my tomato plants and noticed something that has me concerned. There seems to be a fungus or mold at the very base of my "super fantastic" tomato plant. Other than this issue and the slow ripening the plant seems to be doing okay. I haven't noticed this fungus/mold before so I don't know if has just appeared and is spreading rapidly or if it has been there all along. Do you know what it is? Will it spread through the entire plant? Will it spread to the other tomato plants and veggies in this bed? Should I remove the entire plant?

View Answer:

This sounds a lot like Fusarium wilt, but it could also be Verticillium (another fungal problem) or even walnut toxicity (do you have any black walnut trees within 50 feet of your plants?). It might even be excessive watering which is causing the problem.

According to The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale, 1996), you can cut open a stem near the soil line and look for internal discoloration. Verticillium affects the whole plant, while Fusarium will start by infecting individual shoots and then spread. Tomato Fusarium only affects tomatoes, while there are numerous plants which are susceptible to Verticillium. The best thing to do if your plant is suffering from these fungal diseases is to destroy them, so you may want to take a sample to a Master Gardener Clinic for diagnosis before you do anything drastic.

General resources on tomato problems:

Recognizing Tomato Problems from Colorado State University Extension.

Vegetable MD Online from Cornell University.

University of California, Davis Integrated Pest Management has excellent pictures of the insides of the stems, for comparison.

Season All Season
Date 2007-07-25
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Keywords: Wilt diseases, Paeonia

PAL Question:

I purchased a bare root tree peony at the NW Garden Show this year and it was doing just fine, getting to be about 1.5 feet tall until about two weeks ago and the entire plant is now drooping, the leaves quickly sagging. It is in a semi-shady spot that receives morning sun. I water all of my plants once a day unless it has been raining. I am trying to figure out if it is dying, and what I might do.

View Answer:

My first thought is that your tree peony is either responding to drought, or too much water. My own tree peony which is about 12 years old has always been sensitive to excessive heat and drought. It is in a partly shady location, but it has root competition from two nearby conifers. Watering less frequently but more deeply is usually a good idea. A commercial peony site has the following information about this plant's water needs. Excerpt:

"Watering: This is the most common misunderstanding. Tree peonies do not have watering needs like roses or other perennials. They are woody shrubs native to northern China, which receives about 30 inches of rain per year. Once established, tree peonies are drought tolerant plants. Excess water will suffocate the roots and is the leading cause of plant failure. Do not plant near auto-sprinkler systems that keep the soils continuously moist. Do not water until soil is dry below the surface and try not to wet leaves when watering to prevent fungus. Be observant; soil can dry out on top and still be moist 6-12" below the surface. When you feel the soil is dry below the first 4-6" and leaves may droop slightly, water the roots deeply. Climates of hot summer temperatures with little or no rain at all will require more attention to watering then those areas that get some rainfall. Peonies in root control bags will require more watering attention than tree peonies planted in the ground. NOTE: Droopy leaves in the first warm days of spring are caused by an imbalance of the root system and leaf production. If soil has moisture, do not water. This imbalance that will self correct as the plant settles into the growing season. You know this is the cause of the limp leaves if the plant recovers in the evening or early the next morning."

The other possibility is a fungal disease called peony wilt. Here is more information about this problem, from the Royal Horticultural Society. Excerpt:

"Tree peonies can be vulnerable to attack by peony wilt (Botrytis paeoniae), especially during wet springs. Symptoms are wilting of the flower buds, sometimes accompanied by a fluffy grey mould and, later in the season, brown blotches on the leaves. Botrytis forms sclerotia (hardened fungal bodies) in diseased tissue, which carry the fungus over the winter, so it is important to prune out and destroy infected tissues to prevent this happening. Currently no fungicides labelled for control are available."

If you think that the problem may be wilt, and would like confirmation, you can bring samples of the leaves to a Master Gardener Clinic for diagnosis.

Season All Season
Date 2007-07-25
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Keywords: Hamamelis, Botanical nomenclature

PAL Question:

Where does witch-hazel get its common and botanical names? Is it related to hazel?

View Answer:

You ask a great question, and the answer is confusing. The scientific (botanical) name, Hamamelis comes from the Greek words for 'together with' (hama) and 'fruit' (melis), according to A Manual of Plant Names, 2nd revised edition, by C. Chicheley Plowden (George Allen & Unwin Ltd., 1970), and it is so called because "the flowers and the fruit are on the tree at the same time." Or it may be the Greek for "a plant with a pear-shaped fruit, possibly the medlar," according to William T. Stearn in his Stearn's Dictionary of Plant Names for Gardeners (Cassell, 1992). Or perhaps 'melis' refers to melon, as this page from the Holden Arboretum website contends:
"The name Hamamelis is from the Greek hama (together with) and melon (apple or fruit) referring to the fact that the common witch-hazel flowers when the fruit is ripe in fall."

Whether 'melis' refers to fruit, pear-shaped fruit, or melon is not elucidated by An English-Classical Dictionary for the Use of Taxonomists (compiled by Robert S. Woods; Pomona College, 1966), which lists 'carpos' for fruit, 'apioides' for pear-shaped, and 'melopepon' for melon (but meaning apple-shaped, or apple-gourd). The fruit of the witch-hazel is fairly inconspicuous and doesn't resemble apples, pears, or melons, but one could make a case for its resemblance to medlar.

About the common name, Holden Arboretum says, "Witch is a corruption of wice, Old English for lively or to bend. In Great Britain, a divining rod in the hands of a dowser would become 'lively' when it came near an underground water source, pointing to the spot to dig a well. While the 'witch-hazel tree' that these divining rods were cut from in England was an elm, Ulmus glabra, American colonists found a suitable replacement in Hamamelis virginiana, which has since been known as a witch-hazel." Plowden's book offers an alternate spelling of the common name, 'wych.'

Hazel is Corylus, which is in the family Betulaceae, while witch-hazel is in the family Hamamelidaceae. I think the connection between witch-hazel and hazel has more to do with a certain similarity of appearance of the leaves.

Season All Season
Date 2012-05-26
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Keywords: Leaf color, Native plants--Washington, Acer circinatum

PAL Question:

We planted a clump of vine maple last fall and because we were in a hurry (landscaping a new home), we just put in without amending the soil. It is dealing with extremely sandy soil, though we did give it fertile mulch, and gets full sun all day long. It looks okay, but the leaves have been very red all summer, basically what I would expect it to look like in the fall. We've been watering a lot to make up for the sand. What's the story on vine maples? We had a lot of them at our old house, but they were mostly under fir canopies or at least were not in full sun. Any tips on helping this one out?

View Answer:

I wonder if the leaves on your Acer circinatum are evenly red, and if they look scorched at all. Leaf scorch is a problem for maples in conditions of stress. See this information from the HortSense database of Washington State University. Excerpt:

"Leaf scorch on maple has many possible causes. Plants that are under stress, such as drought or heat stress, may not provide sufficient water to the leaf margins, causing the edges of the leaves to turn brown and dry. In some cases, scorch may spread to areas between veins or entire twigs may die back. Trees placed near heat-reflecting surfaces, such as buildings or pavement, often suffer from heat stress. Excessive salts from overuse of chemical fertilizers may cause leaf scorch. Scorch may also be a symptom of damage to the roots or stem."

If the leaves are not scorched in appearance, it is possible their early coloring is the result of some other type of stress, or perhaps the leaf coloration has to do with their being in full sun, in an exposed site. You may find this information from University of British Columbia Botanical Gardens interesting: "The formation of red pigments in the autumn provides protection, preventing the too-rapid breakdown of chlorophyll which could occur in exposed (read: excess light) areas. As you can clearly see in the leaf in the upper right, the bottom-right corner has the pattern of the leaf above. Where the leaf above shaded this leaf, no red pigments were produced. Where the leaf was exposed, bright red anthocyanins were formed. To take this to a broader perspective, vine maple trees in shaded forests and under low light conditions have little need to produce red pigments, as the breakdown of chlorophyll can occur at a modest pace. However, vine maples in exposed sites turn flame orange and red, so that the pigments produced will slow the rate of chlorophyll breakdown."

This article from Minnesota Department of Natural Resources discusses premature fall color in maples. Excerpt:

"Each August brings a few trees that begin the fall color frenzy ahead of schedule. In addition to signaling the change of seasons, these trees are sending a clear signal that they are suffering from some form of stress. Stress can have a wide variety of causes, be mild or severe, or, benign or fatal. In any case, professional tree 'care givers' should be aware that the trees are talking to you. Are you listening?
"Maples are probably the group of trees that most commonly exhibit premature fall color. Sensitive to changes in their environment, maples commonly show early color in years when summer rains are heavier than normal and raise soil moisture to or above field capacity during the period from mid to late summer. The maples that show this characteristic the best are the several species of soft maples (silver and red) that commonly inhabit the shrubby areas around wetlands. These trees commonly begin to show deep, rich purples as early as the first week in August. Maples in communities also commonly display early color due to stress mechanisms more common to the urban environment. Sugar maple, in particular, shows early color due to the stress induced by infection from Verticillium wilt. This disease may occur in nursery grown stock in commercial trade. It is difficult to detect because it is soil-borne, difficult to culture, and commonly not tested-for in the nursery. In addition, Verticillium wilt is a relatively weak pathogen that does not do well on young, vigorous nursery stock. Trees can be infected for many years without showing external symptoms of the disease. When they do begin to show symptoms, one of the first is premature fall color followed in succeeding years by a progressive, if not slow, crown decline and dieback."

Maples in communities that are planted 'just-a-little' too deep often show premature fall color. Again this is more pronounced in years with wet summers. The likely mode-of-action is decreased soil oxygen content. Planting too deep 'smothers' roots reducing oxygen in the root zone. So does over watering whether natural or artificial. The bottom line is stress-induced premature fall color. Remember that stress is (1) caused by many factors, (2) cumulative, and (3) potentially fatal if left untreated.

Season All Season
Date 2007-07-18
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Keywords: Eutrema

PAL Question:

I would like information about growing wasabi in the Northwest, such as how to propagate it, and ideal growing conditions.

View Answer:

We don't have any books in the Miller Library on wasabi propagation, and most general propagation books do not include wasabi (the plant's botanical name is Eutrema, though there is some taxonomic disagreement over the species name, and the genus is sometimes listed as Wasabia). Cultivation of wasabi in this country is a relatively new endeavor, so the more current the source, the better. I did a journal search in Web of Science, and could not find anything on wasabi propagation or cultivation. There may simply be little information out there.

A colleague here in the Miller Library says that wasabi is a notoriously difficult-to-grow plant, and the fact that it requires cold running water throughout the year seems to preclude growing it in a climate which has freezing conditions in winter, unless you are able to protect the plants from frost damage.

Washington State University's publication, "Growing Wasabi in the Pacific Northwest," by Carol Miles and Catherine Chadwick, may be especially helpful to you. There is an earlier article by Miles from WSU's Vegetable Research facility. It was published in PNW Sustainable Agriculture Newsletter in October of 1996.

Purdue University's New Crops site offers the following information on wasabi cultivation. It contains a link to an article on growing wasabi in New Zealand, which has some climate similarities to our region.

This general article on wasabi includes a list of growers. You will notice that several are in the Pacific Northwest.

Although it is not specific to the Pacific Northwest, Utah State University has a concise guide to growing wasabi in the garden.

Mother Earth News also published an article on wasabi cultivation in October/November 2004.

Season All Season
Date 2012-02-08
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Keywords: Rhododendrons--Diseases and pests

PAL Question:

The edges of the leaves on one of my rhododendrons are turning brown and crispy. This condition advances toward the midline until the leaf dies. My older, more established rhododendrons are looking fine. All have flowered this spring.

View Answer:

We can't diagnose the problem via e-mail. However, what you describe could be a couple of things.

It might be marginal leaf necrosis which can be caused by cold damage, and made worse by wind and drought; by drought while the plant is in active growth; by high amounts of salt in the soil, often due to overuse of soluble fertilizers, and seen often if plant is located close to the house, where the eaves prevent rainwater from reaching the soil. Other causes are poor drainage, planting too deep, root damage, root weevils, nutrient deficiency, or disease. (Source: How to Identify Rhododendron and Azalea Problems, Washington State University Cooperative Extension, 1984).

There are descriptions and illustrations of rhododendron problems on the HortSense website of Washington State University Extension.

For comparison purposes, see the lists of diseases and problems affecting Rhododendrons from University of California, Davis Integrated Pest Management Online. To get a definitive answer, it may be a good idea to take samples of the affected leaves to a Master Gardener Clinic for diagnosis.

Season All Season
Date 2007-08-01
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Keywords: Powdery mildew diseases, Perovskia, Vegetables--Diseases and pests

PAL Question:

Last year I planted 25 gorgeous Russian Sage in 1 1/2 gal pots. They were fabulous last year, but barely came back this year. We had a mild winter here in New Jersey, but even so, I know that is not an issue with that plant as I've grown it for years. This year I planted an additional 40 in the same hillside and they are doing phenomenally well. On last year's plants, some have flowered a tiny bit, but none have come back to the size they were and most are so small, they look like they came from a 6-inch pot! Do you have any thoughts as to what I can do to improve the situation?

Also, although we haven't had much rain, I am seeing what I'm assuming is mold on several of my plants: trumpet vine, roses, honeysuckle. The zucchini and cucumbers have been totally decimated so there is no fruit. White is covering the leaves and with the veggies, the leaves are crumbling and disintegrating.

View Answer:

There are a few possibilities for the poor showing of your Russian Sage (Perovskia atriplicifolia) plants. However, without knowing more details about the growing conditions, I may be offering you advice that does not help. If the pots you selected to grow your plants in were made of a thin material, there is a chance you did not provide them with enough protection from the winter temperatures. Planting them directly into the ground can help to avoid this, if it's possible for you to do so in their location.

Depending on the amount of sun and moisture your plants are receiving, poor growth can result. Russian Sage plants like "a well-drained soil and need to have a warm to hot, sunny position" in the garden. (The Cultivation of Hardy Perennials by Richard Bird published in London by B.T. Batsford Ltd in 1994) If the soil is too wet, root rot can occur.

If they are in the proper cultural environment (lots of sun and well-drained soil), then perhaps they are lacking nourishment. The Plant Care Manual by Stefan Buczacki (published by Crown Publishers in New York in 1993), suggests feeding your plants with a general purpose fertilizer in mid-spring and in mid-summer.

As for your second question, I believe what you are describing is a case of powdery mildew. It is a fungus that shows itself in times of dry weather. The main thing you will need to do is destroy all the foliage affected by the mildew. The mildew on infected foliage will spread to new foliage.

Powdery mildew thrives where plants are crowded and there isn't enough air circulation, so give your plants space, a sunny site, and try watering in the morning, and watering from beneath the plants (not over the leaves) so they are able to dry off during the course of the day.

Here is a link to the University of California-Davis, Integrated Pest Management website. You can learn more about this fungus, including host plants, life cycle and management.

Colorado State University Cooperative Extension has some information about powdery mildew as well, including preventative measures and a recipe for making your own baking soda fungicide.

Season All Season
Date 2007-08-02
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Keywords: Tolmiea, Moss gardening

PAL Question:

Can you provide me with information on growing moss indoors? Also, do you know if Tolmiea is known for being fragrant?

View Answer:

Here is an article, "Indoor Gardening with Moss" by Robert Paul Hudson, from the Eugene Daily News. The author provides directions on maintaining a small terrarium with moss.

The web site Bizarre Stuff is another resource. Excerpt:

Mosses can be grown in terrariums fairly easily. Collect moss from an area where it is okay to do so and transport in plastic sandwich bags. Sprinkle with water and seal the bag if you won't be setting up the terrarium right away. Use a large, clean glass jar with a tight fitting lid. Lay it on its side in a shallow box or on a stand so that it will not roll. Place sand and pebbles about 1/2 inch thick in the bottom of the jar. On top of this place some of the soil from the same place where the moss will be collected, or mix a soil of charcoal, light gravel, leaf mold and garden soil. The soil should be level with the opening of the jar. A little sulfur scattered on the soil will help to prevent mold from growing. Plant the moss by pressing it into the soil. Water the terrarium, screw the cover on, and place it in a shady place. If it seems too wet, leave the lid off for a few hours to allow some of the water vapor to escape. Eventually you will get the balance of water just right, and the moss should thrive. The terrarium should sustain itself for several weeks or months without needing additional water if the lid is kept tightly on. If conditions are just right, the moss may eventually send up little stalks. Some of these stalks form spores that will fall to the soil and germinate into new plants.

The January 2007 issue of Better Homes and Gardens has an article, "Pleasant Under Glass," by Suzy Bales. Here is an abstract: The article highlights the fragile beauty evoked by glass gardens or terrariums. Everyday containers such as carafes and vases can make ideal terrariums. Featured in the article is an antique terrarium that becomes a stage for a miniature woodland garden. It has flowering Cape primrose, rabbit's-foot fern, golden club moss and black and dwarf mondo grasses.

The January 2003 issue of Sunset has an article by Kathleen Brenzel, "Serene Greens," on miniature indoor landscapes: Presents ways in creating a miniature indoor landscapes. Use of copper trays in Irish and Scotch moss; Dimension of the ceramic cache pots for mini bog plants; Amount of water used for hyacinth floats.

Now on to Tolmiea. I consulted several reference books and online plant databases, but none mentioned fragrance as a quality for which this plant is known. This does not necessarily mean it has no fragrance, only that it is not notable.

Season All Season
Date 2007-08-02
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Keywords: Fruit trees--Cross-pollination, Cornus mas

PAL Question:

Can you tell me how to grow Cornelian cherry? Do I need more than one tree to get fruit? Also, what kind of soil and fertilizer does it need?

View Answer:

Cornelian cherry, or Cornus mas, is not especially fussy about type of soil, but prefers well-drained moist soil that is somewhat rich. According to Lee Reich's Landscaping with Fruit (Storey, 2009), the tree is at least partly self-fruitful, but planting a second tree (a different cultivar or clone) will increase fruit yield. I don't think there are particular fertilizer needs for this tree, but you can provide a mulch of compost in spring or fall if you wish. Reich says to "plant this tree carefully, keep weeds at bay at least for the first few seasons, water as needed during the first season and you'll have little else to do for your tree beyond enjoying looking at it and harvesting the fruits."

The local website of Great Plant Picks has information about this tree.

Washington State University at Mount Vernon's fruit research center offers a list of cultivars tested in 2007:
Cornus mas

  • "Elegant"
  • "Olga"
  • "Pioneer"
  • "Red Star"
  • "Sevetok"
  • "Yevgenii"

Season All Season
Date 2010-04-17
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Keywords: Larix, Dwarf conifers

PAL Question:

I have purchased a Larix laricina 'Blue Sparkler.' It appears to be a dwarf larch but I can't find any information about it. Could you point me toward a reference?

View Answer:

According to an article by Kathryn Lund Johnson in The American Gardener, volume 87, no. 6. (2008) entitled "Wicked and wonderful: witches' brooms," Larix laricina 'Blue Sparkler' is a witches' broom cultivar. It was introduced in 1993, and is a dwarf deciduous larch with "a dense habit that is reminiscent of miniature fireworks. Its blue green needles turn gold in autumn, then drop. In 10 years, it can grow three feet high and two-and-a-half feet wide."

Witches' brooms are a type of deformity that can occur for a number of reasons, according to the article, including dwarf mistletoes, fungi, viruses, bacteria, and aphids. Witches' brooms on conifers are used as a source for propagating new cultivars. The propagator takes a cutting from the broom, and this 'scion' is "either rooted directly or grafted to young conifers that serve as the 'understock.' When grafting, the wound is given a year to heal. The understock is then removed and a new plant stands in its place." This method was pioneered by Sidney Waxman, a professor of plant science at University of Connecticut, Storrs. He is responsible for developing the 'Blue Sparkler' tamarack you are growing.

Iowa State University has a page of information about the phenomenon of witches' brooms.

Season All Season
Date 2010-04-17
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Keywords: Chamaemelum, Thymus, Ground cover plants

PAL Question:

I am building a stone walkway. What can I plant in the cracks that will take the sun and that I can walk on?

View Answer:

Creeping thyme would be ideal for your needs. It will do well in sun, and can withstand foot traffic. Colorado State University Extension has useful information on groundcover plants for dry conditions.

Leptinella, or brass buttons, is another option.

Chamaemelum nobile likes sun and will withstand light foot traffic.

The website for Stepables, a company specializing in groundcover plants, allows a search by plant characteristics.

Season All Season
Date 2007-07-25
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Keywords: Wind-tolerant plants, Acer palmatum

PAL Question:

I want to find an Acer palmatum cultivar that can manage full sun and high winds. Is this asking too much of the dainty thing? Can you suggest a type, or a source that lists palmatums and their various needs and attributes?

View Answer:

Interestingly enough, Acer palmatum is listed as possessing medium-high wind resistance by University of Florida Extension in their trees-and-hurricanes information.

The following comes from Mississippi State University Extension:
"The U.S. Forest Service conducted a study after Hurricane Camille devastated the Coast in 1969. The study indicated that the best wind resistant trees are compact and have major tap roots. Trees with a tapered trunk have a low center of gravity and are more stable."

I would be concerned about scorching from exposure to hot wind, and damage from winter wind even if the tree is not likely to lose limbs. Here is what J. D. Vertrees's book, Japanese Maples (Timber Press, 2001, 3rd ed.) has to say: "A spot with a constant strong wind will misshape the plant and may burn the leaves. In winter, the wind-chill factor may cause bark and cambium damage (...) In areas of strong marine breezes, leaf damage from salt deposits may occasionally occur. Anyone growing plants under such conditions should be familiar with the necessary protection and the need for periodic washing of the foliage with fresh water."(p. 63)

A commercial nursery, Maple Ridge groups Acer palmatum cultivars by type. University of British Columbia Botanical Gardens offers additional information.

Season All Season
Date 2007-07-25
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Keywords: Propagation, Allium

PAL Question:

Could you tell me how to grow Allium from seed?

View Answer:

I will assume you are propagating ornamental Allium. According to the American Horticultural Society's Plant Propagation (edited by Alan Toogood; DK Publishing, 1999), Allium seeds may be sown any time from late summer to early spring. Seeds should be collected when the flower heads turn brown and before the seedpods open. If you tug gently on the flower stalk and it comes away easily from the base, the seed is ripe. Cover the spot where the stalk was removed with soil to prevent entry to pests. With smaller flowering Allium, you can shake seeds directly into a paper bag (without removing stalks). Sow the seeds fresh, or store them at 41 degrees F, and sow in the spring. Germination time is usually 12 weeks, but in some cases it will take up to a year.

The Royal Horticultural Society says that Allium cultivars may not come true from seed, so you may want to consider alternate methods of propagation, such as by offsets or aerial bulbils.

Season All Season
Date 2007-08-03
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Keywords: Wisteria, Pruning

PAL Question:

Is it all right to cut off the hanging pods from the Japanese Wisteria? Will cutting them have any adverse affects to blooming next year? Some are hanging so long that we keep walking into them! Maybe I should cut them and bring them inside for decoration.

View Answer:

Cutting off the seedpods on your Wisteria is not a problem, just be careful not to cut the stems back too far (unless you are intending to prune, which you can certainly do if you need to control growth) as there may be buds further up which will be next spring's flowers.

Fine Gardening online has a helpful illustrated article on wisteria pruning which includes the following:
"Some seedpods may be left on the vine for winter interest, but just know that if you bring them inside, warm temperatures will cause them to explode."

You may find the following links to general information on care and pruning of Wisteria helpful:

Growing the Beautiful Wisteria Vine from WSU Extension
Growing Wisteria from Ohio State University Extension

Excerpt from an article, "Pruning Vines," originally published on the website of Michigan State University Extension but no longer available online:

Pruning wisteria extensively during the dormant season may encourage rampant vegetative growth the next spring. Instead, in July prune out the long, straggly growth except those branches needed for climbing. This is more likely than anything else to induce flowering. Shoots should be cut back one-third to one-half their length. This will induce them to produce the short spurs that will bear next season's flower clusters.

Season All Season
Date 2007-08-02
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Keywords: Aphids, Betula, Trees--Diseases and pests

PAL Question:

I have just taken over management of the small landscaped yard for my condominium and we have two trees (weeping birches I've been told) in the front that appear to have been infested with aphids. The trees are about 15 feet tall and are located between the building and the sidewalk to the entrance. They have southern exposure. There's a few evergreen bushes around the trees, no grass.

I am not familiar with aphid controls, so have done some internet research, including your very useful site. We want to avoid using pesticides, so from what I've read, the best control is insecticidal soap. Before I try to spray this on the trees I have a few questions I was hoping you could answer. 1. Can you verify that this is aphid damage? 2. It seems to me that the amount of white material on the undersides of the leaves has decreased in the last month. Given that it is getting late in the growing season, is it still worth treating the trees? 3. Does insecticidal soap seem like a good treatment in this situation, and if so do you have any application tips to make sure the undersides of the leaves are treated?

4. Do you have any recommendations for preventative actions to decrease the impact of aphids on these trees in the future?

View Answer:

Birches are commonly afflicted with aphids, and the aphids suck sap and secrete honeydew, which can be a nuisance, and is usually why homeowners contact us. Unfortunately, if your birches are overhanging a sidewalk, it is probably getting sticky from the honeydew. Otherwise, you could probably ignore the problem (except in the most severe infestations).

You can try spraying the aphids off the leaves with a strong jet of water. You can also encourage natural predators. Avoid over-fertilizing, or exposing the trees to lawn fertilizer, for example, as this will lead to succulent new growth which attracts aphids. Make sure the trees are not under any stress, as aphids are more likely to feed on a weakened tree. You may be able to avoid using the insecticidal soap as a control. If you do use it, you are correct that you need to reach all leaf surfaces, which is labor-intensive. Some of these soaps can cause damage, so it is always a good idea to test any such spray on a small area before coating the whole plant. An article by Colorado State University Extension provides information on insecticidal soaps. Aphids go through many generations in a year, and their eggs can overwinter.

Washington Toxics Coalition has created a document on managing aphids in the landscape.

Here are additional links on aphid control: Aphids from University of California at Davis
Managing Aphid Problems without Pesticides from the Northwest Coalition for Alternatives to Pesticides

Season All Season
Date 2007-08-01
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Keywords: Woody plant propagation, Propagation, Abelia

PAL Question:

How would you propagate Abelia x grandiflora?

View Answer:

According to the American Horticultural Society's Plant Propagation edited by Alan Toogood (DK Publishing, 1999), Abelia may be propagated from softwood cuttings in spring, from greenwood cuttings in late spring, and from semi-ripe cuttings in early to late summer. "Cuttings... root very readily in a closed case or mist bench. Softwood cuttings from the first flush of root growth in 2-4 weeks. In colder regions, do not pot greenwood cuttings taken after midsummer; prune cuttings into a bushy habit, but allow new growth time to ripen--if not well established, they overwinter badly. Keep semi-ripe cuttings taken in late summer frost-free. Plants flower in 1-2 years."

Here are links to general information on propagation from cuttings:

Plant Propagation by Stem Cuttings: Instructions for the Home Gardener, from NC State University
Propagating Plants from Stem Cuttings, from Rainyside Gardeners

Season All Season
Date 2007-08-01
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Keywords: Lupinus, Propagation

PAL Question:

I moved to New Hampshire from Missouri and want to grow lupines. Having purchased some plants, I have enjoyed many blooms. After the bloom, the flower turns into what looks like a pod with seeds. Can I replant those seeds in order to propagate them for next year, or when is the best time to plant them? Also for the remaining foliage on the plant, what should I do to maintain it? Continue to water it and give it MiracleGro for nutrients?

View Answer:

According to the American Horticultural Society's Plant Propagation edited by Alan Toogood (DK Publishing, 1999), lupines may be propagated from seed between early and mid-spring. (Other methods of propagation include stem cuttings taken in mid- to late spring). Lupine seeds require some special treatment, as described by Sustainable Urban Landscape Information Series from University of Minnesota:
"Moisture is important to seed germination. Some seeds are protected by a tough seed coat. Some must be soaked in water to soften the seed coat prior to germinating. Other seeds must have their seed coat nicked or pierced (scarified) in order to allow moisture to reach the seed, causing it to expand and break through the seed coat; two examples are in the legume family - sweet peas (Lathyrus species) require soaking, and lupine (Lupinus species) require scarification.

The following information from University of Washington should apply to your lupines, not just our native lupines. It suggests collecting seed from June to August, storing the seed in the pods inside paper bags, and then scarifying them prior to soaking and sowing (in spring or fall).

Lupines should do well in zones 3 to 8, depending on the species. More information on growing hybrid lupines can be found here, including suggestions on fertilizing. Choose a complete slow-release organic fertilizer instead of synthetic fertilizers like MiracleGro, which may be too high in nitrogen.

When flowering is finished, you can cut the plants down to the ground, and you may still see a second burst of growth. There is no need to water when the plant is not in active growth. (In our Northwest climate, the leaves tend to look mildewy by this time of year, and you would want to cut them back anyway). Rainyside Gardeners, a Pacific Northwest website, has additional information.

Season All Season
Date 2007-08-01
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Keywords: Scale insects, Euonymus, Insect pests--Control

PAL Question:

Have you heard about a problem with Burning Bush (Euonymus alatus) getting a mildew this year? The leaves have turned yellow green with small spots of lighter yellow discoloration.

View Answer:

Powdery mildew is a common and usually not life-threatening problem with Euonymus. Make sure the plant has good air circulation, and be sure to clean up and destroy fallen leaves which are infected. However, the symptoms of this fungal problem would be whitish coating on the leaves, rather than yellowed leaves. This makes me wonder if it is a different problem such as scale (which is actually an insect). Check and see if there are small bumps on the leaves or stems. Scale can cause yellowed leaves. If your plant has a small infestation, you can try scraping the scales off with your fingernail, prune out the most infested parts of the plant, and then apply dormant oil to the trunk and branches before growth starts next spring, or apply superior oil during the growing season. There are also other fungal and bacterial problems that could be causing the spots.

See this fact sheet from Penn State for more on Euonymus scale.

Here is a link to additional information, which comes from University of Illinois Extension. Excerpt:

Burning bush (also called Winged Euonymus): Euonymus alatus

Cold injury - Winter injury may be caused by very low temperatures as well as drought stress. With excessively low temperatures, the moisture in the cells freezes (due to chemical compounds in plants, moisture freezes at various degrees below freezing). Drought stress already has resulted in limited moisture in the plant cells. Dry, freezing winds during the winter reduces the moisture level even farther, often resulting in dead plant tissue. Diseases can help magnify or increase susceptibility to winter kill. Nectria canker kills the sapwood tissue thus reducing or even cutting off moisture to tissue further out on the plant. Winterkill also makes plants more prone to infectious diseases and insect problems.

Dieback/canker - See bridal wreath spirea. In addition Botryosphaeria dothidea will infect and kill for similar reasons.

Winged euonymus scale - Lepidosaphes yanagicola occasionally occurs in the southern half of Illinois on burning bush. It is an armored scale. And will attack several trees as well. This scale can cause premature leaf drop, branch die back and cause the plant to become more prone to winter injury. It is found between the "wings" - the bark ridges. It does not move to the plant's leaves. The scale over winters as an adult and lays its eggs in June. Eggs may be laid for up to a month. Mating occurs before frost.

Euonymus scale - Unaspis euonymi - females are black and males are white. The scale causes the foliage to develop yellowish green spots. Heavy infestation results in early foliage drop and often stems are killed. Eggs survive by over wintering in the female body. The eggs hatch about early June in Northern Illinois. Crawlers emerge and move onto new growth or can be blown by wind to other plants.

Since I cannot diagnose the problem remotely, it makes sense to take plant samples to a Master Gardener Clinic.

Season All Season
Date 2007-08-08
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Keywords: Cupressus, Moths, Trees--Diseases and pests

PAL Question:

I haven't been able to find much about control of cypress tip moth on true cypress (Cupressus). I'm looking for a non-toxic control instead of the WSU recommendation of Orthene. Would Neem possibly work? Spinosad? Both are registered for leaf miners (fly larvae), but this is a moth larvae. Bt won't work because the larvae are inside of the foliage. What's the best timing for a non-toxic? WSU recommends controlling the adults in July-August.

View Answer:

University of British Columbia Botanical Garden's forum has this to say:

"In the west, cypress tip moth sometimes infests cypress (Cupressus and Cupressocyparis) and false cypress (Chamaecyparis); those are also sometimes called cedars. In the east, cedar often refers to Juniperus (red cedar), Thuja or Chamaecyparis (white cedar); all are subject to bagworm infestations and various tip-miners. In the west, timely shearing is the most effective way to control cypress tip moth, and this may also be a tactic in other parts of North America.

"In many cases, infestations occur because there are few natural enemies about to reduce pest levels. Sometimes, pests are attracted to plants that are already weakened by stress. Healthy plants and diverse plantings, together with a reduction in pesticide use, will over time, increase beneficial organisms which will in turn reduce pest levels. Spraying to reduce pests generally affects beneficials to a greater degree than the actual target pest. This is because pest species often have a greater capacity to rebound -- they often reproduce faster, have a greater tolerance for pesticide residues and have a greater capacity to become resistant to pesticides."

Oregon State University's IPM site only mentions chemical controls.

From an online forum, 'Horticulture Guy:'

Q. I have a row of 16 - three year old "Emerald Green" arborvitaes. I suspect they have arborvitae leafminer (cypress tip moth). I have noticed the moths before, but now there are more and I just recently noticed brownish-yellow tips on a couple of the trees. All of them have lots of needles falling from the interior. My problem is that I have received conflicting reports about the proper time to spray for them, and is there anything I can do in the meantime to lesson the damage? Thank you! Linda Brieger - Tacoma, WA

A. The way to gain control over any pest population is to know its life cycle. Spraying is geared toward eliminating the adult form of the insect, which is a moth as the second of the two common names indicates. The most likely reason you may see conflicting reports on when to spray the moths is because of varying times the moth may emerge in different regions where they are present. They are generally active in our area from April to June with a peak of activity in May. The moths lay their eggs during this period and the eggs hatch and then burrow into the needles of the host plant. According to the WSU extension the adult moths are silver-tan and approximately 1/4" in length. External sprays won't have an effect on the larvae once they burrow so you need to spray weekly during this period to catch the larvae as they hatch. Systemic insecticides are able to kill the larvae once they are in the host. You can limit systemic insecticide spraying to one application near the beginning of the activity since they generally remain effective for some time (see labels for instructions). As far as "in the meantime" a sprayless solution is to prune out and destroy infected parts of the host now so that there are less moths in the spring. You can also keep an eye out in the spring for the white cocoons that form after the larvae exit the host to become adult moths. You can remove these as well.

University of California Integrated Pest Management suggests that proper cultural care and removal of susceptible plants is the answer. Excerpt:

Provide proper cultural care to keep plants vigorous. Prune out and dispose of foliage infested with immature leafminers to restore the plant's aesthetic appearance and provide some control. Consider replacing plants especially susceptible to the cypress tip miner. High populations and damage can be reduced on established plantings by applying a broad-spectrum, persistent insecticide such as acephate on susceptible varieties when adult moths are active. Beginning in early spring, examine foliage tips for the cocoons. When these appear, vigorously shake foliage and watch to see if silvery tan, tiny moths fly up then settle back on the foliage. One application to foliage can be made when a large number of tip moths appear, between March and May in California. This reduces browning next season.

You could try using the Neem oil (instead of the more toxic alternatives) although I did not find any information specifically suggesting this as a control for cypress tip moth. The WSU book, Pacific Northwest Landscape IPM Manual (2002) suggests natural parasites which attack this species of insect, but they do not specify the identity of these predators. They state that there are no "biorational pesticide management options" for this pest.

Season All Season
Date 2007-08-10
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Keywords: Campsis

PAL Question:

I was given a Campsis radicans 'Galen.' I've heard this vine can be invasive. Do I dare plant it? What do I need to be wary of?

View Answer:

Campsis radicans is certainly aggressive and potentially invasive in some areas, but to what degree depends on where you live. It is listed as a weed in the Northeast, the South, and Kentucky. The Missouri Botanical Garden has another profile of this plant.

I have seen it growing here in Seattle, and it seems to do well but perhaps not so well that it is a major concern in this area. Since it spreads by runners and seeds, keep it trimmed and do not let the flowers go to seed. Wear gloves when handling it, as it can be a skin irritant.

Season All Season
Date 2007-08-15
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Keywords: Asparagus, Mulching

PAL Question:

Can cotton hulls be used as mulch on asparagus?

View Answer:

Here is what Stu Campbell's book, Mulch It! (Storey Books, 2001) says about cottonseed hulls as mulch:

These hulls can be used most effectively around plants such as beans, which are suited to wide-row planting. Apply a 1- to 2-inch layer. Or you can wait until the plants have grown 3 or 4 inches high, then sift the mulch down through the leaves... Cottonseed hulls have a fertilizer value similar to, though not as rich as, cottonseed meal. Because they are so light, the hulls blow around in the wind.

Campbell discusses mulching asparagus with a choice of hay, leaves, straw, old manure, and compost for winter protection. You can leave these mulches in the spring, and the tips will emerge through the mulch. If you wish to extend your growing season, he recommends dividing your bed in 2 parts in spring. Mulch one half heavily with fine material like cocoa hulls, leaf mold, or ground corncobs. Leave the other half unmulched until shoots break through the mulched side. Then mulch the unmulched side. The half which was mulched earlier will bear a few weeks later than the other half.

The National Sustainable Agriculture Information Service has a web page on organic growing of asparagus crops which mentions other types of mulch (such as winter rye as a dying mulch and perennial ryegrass and Dutch white clover as living mulches) for this crop, applied at different times.

It sounds to me as if the main drawback with cottonseed hulls is their light weight. Otherwise, they should be acceptable as a spring mulch.

Season All Season
Date 2007-08-15
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Keywords: Orchidaceae (Orchid family)

PAL Question:

All but one of my orchids are blooming this season! What could be the cause of the one orchid not blooming?

View Answer:

First of all, congratulations that you have all but one of your orchids blooming. Orchids are plants with very particular needs, as you well know. I have found two possibilities as to why your one orchid will not grace you with its flowers: light and space. However, there are other possibilities as well, which I will try to address.

Perhaps this one plant is not receiving the amount of sunlight it needs to bloom and the others are. Are all your orchids the same species or variety? If so, are they all in the same area of your house; i.e. same window? If they are not the same species or variety, then they may require different amounts and levels of intensity of light. Are they growing in a window with natural light or are you growing them under artificial light? If you are using artificial light, orchids do require dark as well as light. Orchids "should not receive more than 14 hours of artificial light a day. More than that will prevent them from blooming." (Orchid Growing Basics by Dr. Gustav Schoser, Sterling Publishing Company, 1993)

Are you using a fertilizer? If so, and the first number is a lot higher than the second or third (such as 15-5-5), it is likely that the plant is receiving too much nitrogen. This will do wonders for the green leaves but nothing to promote flowering. A fertilizer with the numbers closer together (such as 10-12-10) will be more balanced and would be recommended. Are you monitoring the temperature? "The effects of temperature changes are most clearly observable in the Cymbidium orchids. Flower production begins when daytime temperatures are about 68 degrees and nighttime temperatures are around 50-57 degrees. Phalaenopsis schilleriana and its hybrids will only bloom when the nighttime temperature is under 68 degrees for at least 2-3 weeks." (Orchid Growing Basics)

Here is an excerpt from a frequently asked question and answer web page from a commercial grower: beautifulorchids.com.

Q: I am growing my phalaenopsis orchid in the house but they never bloom. What can I do?

A: The most common reason for any orchid not to bloom is insufficient light. Move your phalaenopsis plants to a window where they will receive strong, but indirect light (near a south-facing window is ideal). You might also try lighting your plants with a fluorescent light fixture placed about 1-2 feet above the foliage. Give up to 12 hours of supplemental light per day. Phalaenopsis will also develop flower spikes in response to a cool period of about four weeks with night temperatures of 55F. After the cool treatment, raise the night temperature back to the normal 60-65F minimum. See if these changes to your growing conditions help to stimulate your plants to bloom.

Another page on the same site more clearly defines good vs. bad light. They explain that too little light may prevent the plants from blooming. They also list specific orchids that prefer low light and those that prefer moderate to high light.

The Brooklyn Botanic Garden All-Region Guides: The Gardener's Guide to Growing Orchids (2004) Handbook #178, (partially available online) has a lot of good information regarding light requirements on a variety of orchids. It is noted in this book that "light is undoubtedly the most important factor in determining whether or not an orchid will flower."

Also, there is a possibility that the one orchid has outgrown its pot faster than its companions and has a need for more space (and possibly more nutrients). "Most orchids usually only bloom from new growth" (Your First Orchids and How to Grow Them published by the Oregon Orchid Society, Inc 1988). "An orchid is in need of repotting when the leading pseudobulb or growth has reached the rim of the pot and there is no room for future development. (The Gardener's Guide to Growing Orchids by Wilma and Brian Rittershausen, David and Charles Publishers 2001) If you are getting new shoots but they are growing over the edge of the pot and breaking off, this would also be a sign for the need to repot.

The Gardener's Guide to Growing Orchids by Wilma and Brian Rittershausen, and The Brooklyn Botanic Garden All-Region Guide and Orchid Growing Basics by Dr. Gustav Schoser, offer good directions on repotting. The Schoser title even offers recipes on how to make your own potting mixes.

Something that may be of interest to you, if you are not already aware of it, is a web forum on orchids at allexperts.com. Hundreds of questions asked by novice orchid growers are answered by orchid growing experts.

Season All Season
Date 2007-08-22
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Keywords: Symphyotrichum, Perennials--Care and maintenance

PAL Question:

Our Asters are green and getting ready to bloom but the lower 8" are "rusty" or burnt looking. Did our bark mulch hurt them? Too much fertilizer? This is their third year in the same spot.

View Answer:

There are quite a few potential causes of the rusty leaves you are seeing. It might be entirely normal, as mature Asters (renamed Symphyotrichum) can start looking a bit ragged in late summer. It could be due to excessive heat, overwatering (symptoms include yellowing and dropping of lower leaves), or fertilizer burn (Asters are sensitive to soluble salts in chemical fertilizers). It could be a fungal disease, rust, or Aster yellows, a common disease caused by a microscopic organism (phytoplasma) and spread from plant to plant by leafhoppers. With Aster yellows, you would notice a loss of green in the leaf veins, and yellowing of new leaves. Sometimes, infected outer leaves turn a rusty or reddish purple color. A good general practice to keep your Asters looking full and less leggy is to cut them back by one-half to two-thirds when they have reached 12 to 16 inches in late spring/early summer. (Source: The Well-Tended Perennial Garden by Tracy DiSabato-Aust, Timber Press, 1998).) Here are links to resources which describe other possible causes of the leaf problem.

Connecticut Agricultural Experiment Station

Missouri Botanical Garden

To determine the exact cause, it might be worth bringing a sample to a Master Gardener Clinic.

Season All Season
Date 2007-08-18
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Keywords: Corylopsis

PAL Question:

Our Spike Witchhazel has burnt leaves throughout the plant on the tips. What could be the cause of this? This is its third year in the same spot with full sun.

View Answer:

Are you referring to Corylopsis (sometimes known as Spike winterhazel or Buttercup winterhazel), or to a Hamamelis? (They are in the same plant family, but look quite different). Here are some pictures for comparison:

Corylopsis

Hamamelis

Hamamelis family

Corylopsis leaf edges do have a tendency to get sunburned in full sun and windy sites. They prefer a partly shady spot, and organic, acid, well-drained soil, although they will do well enough in full sun (except for the burnt leaf edges). Again, though, I would be concerned about fertilizer burn as well. I never use fertilizer of any kind, just the occasional addition of organic compost, on my Corylopsis, and it does nicely in a mostly sunny spot.

Season All Season
Date 2007-08-15
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Keywords: Woody plant propagation, Magnolia

PAL Question:

I have a Magnolia wilsonii in my garden, and this year there is a definite profusion of seed that followed a long flowering season (I'm collecting more every day). What is the best way to sow and grow these?

View Answer:

According to the American Horticultural Society's Plant Propagation, edited by Alan Toogood (DK Publishing, 1999) you can collect fresh seeds in the fall, and thoroughly clean them (the book recommends using a fungicide to prevent rot or damping off). To extract the seeds, gather the ripe cones and dry them until the fleshy fruits come away. Soak them in warm water with liquid detergent for a couple of days to remove the outer coating. Once softened, drain the water. Remove any flesh still attached, and dry the seeds with tissue. Sow fresh and overwinter in a cold frame, or mix with moist vermiculite, sand, or peat, and store in a plastic bag in the refrigerator for 2 months before sowing. Seedlings may be transplanted the following summer, and put back in the cold frame for a second winter.

Another method is to stratify the seeds for 3-6 months at 41 degrees Fahrenheit, sow under cover in spring with bottom heat (68 degrees) for germination to take place in about a month. It will take plants grown from seed from 3 to 10 years to flower, but some species take much longer.

Texas A & M University's horticulture department has an article on starting Magnolia from seed. The article focuses on Southern magnolia, but should still be relevant. Here is an excerpt:
"The seeds should be collected as soon as possible after the fruit is mature which is usually mid-September or early October. The cone-like fruit should be spread out to dry for several days until they open. The seeds can then be shaken from the dried cone or fruit.
"If the seed is to be kept for any length of time, the red pulp should be allowed to dry enough to lose its fleshy character, placed in sealed containers and stored at 32 to 41 degrees F. If stored over winter at room temperature seed will lose its viability. The seed should be cleaned before planting or stratifying. To remove the fleshy seed coat, soak the seed overnight in warm water. Remove the seed coat by rubbing against hardware cloth or window screening. After cleaning, the seeds should be sown immediately or stored for 3 to 6 months at about 40 degrees F and planted in the spring. An excellent way to stratify seeds is to use a polyethylene bag and place alternating layers of a moist medium such as a sand and peat mixture and seeds in the bag. Tie the top of the bag and place in a refrigerator at about 40 degrees. The medium should be just moist enough to stick together but not so wet that it will drip if squeezed by hand.
"Whether sown in the fall or stratified in the refrigerator and sown in the spring, the seeds should be covered with about l/4" of soil and mulched to prevent drying. Seedbeds should be kept moist until germination is complete. Partial shade should be provided the first summer for seedlings."

Season All Season
Date 2007-08-24
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Keywords: Pruning trees, Malus domestica

PAL Question:

Could you provide me with information on pruning Red Gravenstein?

View Answer:

I did not find a simple answer to your question about pruning Red Gravenstein. It seems that pruning is key, however, in controlling whether the tree fruits annually or biennially.

The book The Best Apples to Buy and Grow edited by Beth Hanson (Brooklyn Botanic Garden, 2005) has this to say about the Gravenstein apple: Prune and thin to control its tendency to bear a crop biennially.

From the book Apples for the 21st Century by Warren Manhart (North American Tree Company, 1995):

Classified as a biennial bearer, and understanding of its genetics can lead to getting some apples almost every year. Gravenstein is a triploid with 17 extra chromosomes, which means it is nearly sterile, incapable of very much self-pollination. In pioneer times it was typically planted with the old Tompkins County King, another triploid of fine flavor. The East Malling Research Station near Kent, England suggests that triploid varieties should have pollen from two viable pollenizers to properly set seeded fruit and to pollenize each other as well as the triploid.

The author further discusses not grafting to any rootstock larger than M9, M26, or M& unless you want to harvest fruit 20 feet off the ground.

From a contributor to a discussion on Rainyside Gardeners, a local gardening site:

"We don't have a Gravenstein, but we do have 7 other varieties of apples. Gravenstein bear heavily every other year. They should be pruned annually during dormancy. A simple rule of thumb is, anything that grows straight up or crosses another branch has to go. The straight up growths are called water sprouts, and take energy away from fruit production. Apples need to be thinned. One apple per cluster--remove the rest, save the largest one and pick off all the others. Apples should be at least two inches apart."

The book Training and pruning apple and pear trees by C.G. Forshey, D.C. Elfving, and Robert L. Stebbins (American Society for Horticultural Science, c1992) recommends using the central axis or French axe form for Gravenstein apple trees. Here is a description of this method:
"Vertical Axis. The vertical axis, sometimes called the French axe or the central axis, was developed by J. M. Lespinasse in France, and has performed extremely well throughout North America (Table 1). This system requires leader support to a height of 8 feet to 10 feet above ground and minimal pruning is used to develop a tall conical shape (Fig. 3)."

Another description from the University of California Santa Cruz Agroecology program:

Vertical Axis or French Axe

Features:

  • Tree Height -10'-14'
  • Spread at Base - 5'-7'
  • Space between Trees - 5'-6'
  • Tree Density - 500-700 trees/acre
  • Rootstocks - Mark, M9, M26, M7, M106
  • Support - Individual pole or wire trellis
  • Labor Needs - Low; very little pruning; all operations can be done from the ground
  • Cropping - 2-4 years

This system features tall, narrow trees. The aim of this system is to let the tree achieve a natural balance between fruiting and vegetative growth, to reach its ultimate height very quickly (2-3 years), and to come into fruiting early. The vertical axe features almost no pruning in the early years. As with the slender spindle, the aim is to establish a permanent lower tier of branches that are trained to a horizontal position and left long (unpruned). Because the leader is not headed (even at planting), the tree form is very narrow and height is achieved quickly.

Above the lower tier of branches, weak to moderate lateral branches occur randomly. This system also features fruit-bearing on the main leader, which eventually slows tree height, as fruiting is usually more effective than pruning at dwarfing trees. Eventually the leader is pruned into older lateral wood. As the branches in the top part of the tree extend later-ally beyond their desired length of 2-3 feet, they are thinned out or renewed by cutting back to a stub (1-2 buds). The disadvantages of this system are the height of the tree, which requires ladder work, and overly vigorous branches high in the tree, which can shade the lower portions of the tree.

The following article from Alameda County Master Gardeners describes how to prune tip-bearing apples (and pears). This might be of interest to you because Gravenstein is both tip-bearing and spur-bearing.

The Home Orchard Society site has an online forum for submitting questions as well.

Season All Season
Date 2007-08-26
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Keywords: Paeonia, Propagation

PAL Question:

I have a tree peony that started as a seedling from a plant of a friend gave me 8-10 years ago. I would like to try to propagate mine from seed. From the little I've read, it seems this is a difficult process. Can you help me?

View Answer:

I believe you are correct that propagating tree peonies from seed may be a little challenging. It can be done, but home gardeners may find it easier to propagate by grafting, which is described by a link at the end of this answer.

The American Horticultural Society's Plant Propagation, edited by Alan Toogood (DK Publishing, 1999)rates seed propagation of deciduous tree peonies as moderate in level of difficulty. Another thing to bear in mind is that it will take several years before you see flowers on your new plants. In [late] summer, you would sow fresh seeds in pots and "provide two periods of chilling, such as two cold winters, with warmth between. Seeds are doubly dormant (roots emerge in the first year and seed leaves in the second). Guard against mice: they love the seeds."

Another description of propagating from seed may be found in Jekka McVicar's book Seeds (Lyons Press, 2003):

This seed has a double dormancy, producing roots in its first year and leaves in its second. It needs two cold periods, with warmth in between.

Collect ripe, fresh seeds in early autumn. Sow individually in pots, using standard soil-less seed mix, either peat or peat substitute mixed with coarse horticultural sand. Mix to a ratio of 1 part soil-less mix + 1 part sand. Cover with coarse grit, then place outside exposed to all weathers. Visible germination occurs during the second spring. Grow on in a cold frame for 2 years before planting out.

Excerpt on propagation methods from Plants for a Future database:

Seed - best sown as soon as it is ripe in a cold frame.When sown fresh, the seed produces a root about 6 weeks after sowing with shoots formed in the spring. Stored seed is much slower, it should be sown as soon as possible in a cold frame but may take 18 months or more to germinate.The roots are very sensitive to disturbance, so many growers allow the seedlings to remain in their pots for 2 growing seasons before potting them up. This allows a better root system to develop that is more resilient to disturbance.If following this practice, make sure you sow the seed thinly, and give regular liquid feeds in the growing season to ensure the plants are well fed. We usually prick out the seedlings into individual pots as soon as they are large enough to handle, and then grow them on in a cold frame for at least two growing seasons before planting them out when they are in growth in the spring.

The Heartland Peony Society has an illustrated tutorial on grafting tree peonies, should you wish to try this method.

Season All Season
Date 2007-09-01
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Keywords: Prunus persica, Fertilizers

PAL Question:

We have a white peach tree that was just OK this year. I am wondering what I can do to get the most out of it next year - what is the best fertilizer for peaches?

View Answer:

According to Sunset's Western Garden Book of Edibles (2010), peach trees may be fertilized with a 10-10-10 complete fertilizer (the numbers correspond to N-P-K, nitrogen, phosphorus, potassium) at bud break in late March. "Give young trees 1/2 pound per year of age and give mature trees up to 5 pounds (for full-size, full-grown trees). Spread fertilizer evenly over the entire root zone."

Washington State University Extension has general information on fertilizing for home orchardists. Here is a relevant excerpt:

"Nitrogen is not needed in most of western Washington since we have such high levels of organic matter in our soil, and it is continually released during the summers. Nitrogen controls growth. With excess we get rank growth. Fruit maturity is delayed; and storage life of apples and pears is reduced. Peaches need more nitrogen so applications may be necessary."

Season All Season
Date 2011-10-06
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Keywords: Rosaceae (Rose Family), Rhododendron, Fertilizers

PAL Question:

Is it okay to fertilize my rhodies, azaleas, and roses in September? I missed doing it in August.

View Answer:

Generally speaking, it is best not to fertilize your shrubs after mid-summer. The tender new growth that results is susceptible to frost, disease, and insects just at the time of year when the plant is beginning to shut down. This is also true of roses, which are even more tender and susceptible than rhododendrons and azaleas.

An article by Terri Richmond (British Columbia) on the American Rhododendron Society website, entitled Fertilizing Rhododendrons the Organic Way supports the practice of fertilizing in spring. (Keep in mind that azaleas are in the same genus as rhododendrons.)

Oregon State University Extension suggests that budbreak in spring is a good time to fertilize roses, just as new growth is beginning. Stop fertilizing in late summer. Oregon State University also weighs in on fertilizing rhododendrons (if needed, in spring shortly after flowering, and preferably with organic fertilizer).

Season All Season
Date 2007-09-07
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Keywords: Weed control, Rosaceae (Rose Family), Mulching

PAL Question:

We recently had a large blue spruce tree cut down and had the stump ground. Would the resulting sawdust be a good mulch for roses?

Also, what is your opinion of using a pre-emergent herbicide for weed control in our rose bed?

View Answer:

Sawdust has high carbon content and may rob soil of nitrogen and moisture. It is also recommended for acid-loving plants and may be problematic for roses. There may also be compaction problems with sawdust, so it may need to be combined with other mulching materials to improve water penetration. Sawdust also decomposes slowly and compacts (Source: Mulch It! by Stu Campbell, Storey Communications Inc., 2001).

You may also be interested in two articles by Linda Chalker-Scott. In Wood chip mulch: Landscape boon or bane, she discusses the pros and cons of wood chip mulch. She also comments on sawdust in an article called The Myth of Pretty Mulch.

If you had spruce chips, they would be fine for mulching roses. Avoid letting mulch touch the main stem; the goal is to pile it on the root system away from the stem. You can remove it in the spring, or at least be sure that it's not too deep. While mulch protects from cold in the winter and drought in the summer, if it's too deep, water cannot get to the root zone of the plant.

I would recommend that you avoid chemicals, as I find that you have to pay more attention when you use them than if you just wander through the garden now and then and pull all the weeds you see.

Pre-emergent weed controls never provide complete weed control. The most important thing to do is weed the area first, as pre-emergents only control weeds that have NOT sprouted. And if you have lots of seeds in the soil, don't expect weed killer to eliminate them all. If water is required, beware of too much water (i.e., rain) that can wash away the herbicide.

Rather than use a chemical, I would weed the area now and then apply mulch. In addition to protecting the roots and soil, the mulch will suppress weeds, possibly until spring. You will have to watch for weeds that do sprout and be sure that you don't let them go to seed. Otherwise, you will set yourself up for lots of future weeding. Chemicals don't really help in situations like that, as you have to time their application perfectly. Hand weeding and mulching--well timed--can work better than any herbicide.

Season All Season
Date 2007-09-07
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Keywords: Acer palmatum, Transplanting

PAL Question:

I need advice on moving a Japanese Maple tree. The tree is 10 feet tall, and has begun to grow unevenly because it was planted too close to a very large wisteria in front of our house. Ideally, we would only move it 8-10 feet, as there is a wide open space with lots of sunlight just east of its current home. I don't know how deep the Japanese Maple typically roots, or how difficult this may be, but any information you could provide would be very much appreciated.

View Answer:

According to the book Japanese Maples by J. D. Vertrees (Timber Press, 1987), Japanese maples do not have deep, tap-root structures, but are mainly a fibrous root network which stays in the upper level of the soil. As they mature, however, there will be roots going deeper, so if you are planning to move the tree, you will want to be sure to get as much of the root ball as possible. If the tree is not too old, it should be easier. Make sure to water the tree well and prepare the new site before you begin digging carefully.

The Royal Horticultural Society has general information on moving mature trees and shrubs which may be of use to you, keeping in mind that fall is a good time for you to move a tree here in the Northwest.

You can also contact a certified arborist for advice. For a referral, contact Plant Amnesty. You can also go directly to the local chapter of ISA, the International Society of Arboriculture.

Season All Season
Date 2008-02-08
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Keywords: fasciation, Mutation

PAL Question:

The ends of some of my Daphne odora branches look like several branches fused together. What causes this, and is there something I should do?

View Answer:

What you are describing sounds like fasciation, which is a kind of genetic mutation. Professor T. Ombrello of the department of biology at Union County College has a brief explanation of this condition.
Excerpt:
"One interesting type of mistake that is occasionally found in plants is known as a fasciated or crested growth form. It is usually the result of a growing point changing from a round dome of cells into a crescent shape. Subsequent growth produces a flat stem. In some cases fasciation is the result of several embryonic growing points fusing together, with the same flat-stem appearance. [... ] What causes plants to produce fasciated stems? For the most part, we just don't know. Fasciation has been induced experimentally by applications of plant hormones, severe pruning, wounding, and atypical day lengths. Most, however, appear by chance with no obvious cause."

University of Arkansas Extension addresses the phenomenon of fasciation.

Possible causes for this condition:

  • bacterial infection
  • inherited genetic trait
  • herbicide, insect, or physical damage to the growing tip
  • garden conditions that favor rapid growth
  • spontaneous mutations

You don't need to do anything, unless you would like to remove the odd-looking growth. You may want to look into whether herbicide has been used, or if there have been insects feeding on your Daphne. Also, avoid over-fertilizing, which could promote excessively fast growth.

Season All Season
Date 2011-04-09
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Keywords: Ficus carica, Pruning trees

PAL Question:

We recently moved into an old house with a huge fig tree in the back. We just missed this whole season's crop because I was waiting for them to turn brown but the birds got them all first. Then I saw some green figs for sale in the grocery store and it appears that some varieties don't turn brown. Is this true or did mine not ripen? Also, the tree is probably close to 30' and we'd like to add a screened-in porch under part of it. I'd really like to keep the tree and a good bit of fruit but I want it to grow more in the other direction. I've read that "hard pruning" is encouraged, but does that really mean cutting down a thirty foot tree? Do I need to do it in stages? What's the best size and shape and how do I get it there?

View Answer:

There are different types of figs, and some are green, some are brown, some are purple, as the images on the commercial site of Adriano's Fig Trees illustrate.

Figs should be picked when ripe, as they will not ripen off the tree. The California Rare Fruit Growers site has good general information on growing figs.

As for pruning, the best time to prune is late winter/early spring. To control height, open the center of the tree and remove any dead wood or drooping branches. I don't think radical pruning is the standard practice in maintaining a fig tree. University of Arizona article on growing figs describes pruning practices for several different varieties of fig.

Most pruning is best done when the tree is dormant, during the winter when it is leafless. Even during the spring and summer, however, you can start by removing all branches and stems that are obviously dead.

The rest depends on how your tree is growing (single trunk or multi-stemmed), what kind of results you would like (how large, small or what shape) and how long the tree has been unpruned. Our rule of thumb is to go by thirds. Remove about a third of the wood that you would eventually like to have gone. On multi-stemmed figs that are becoming large, we recommend selecting a few oversized stems and thinning those out to the ground, rather than "heading" all the branches to stubs. Let the tree rest for the summer and see what new growth appears. We recommend keeping fig trees small enough that all the fruit can be easily reached from the ground but in some areas of the south and southwest, folks treasure the deep shade of the larger figs. The final shape and size are up to you.

This article by Bunny Guinness in the British newspaper the Telegraph also describes how to prune an older fig tree. Excerpt:

"Figs really are a lazy man's fruit and, once they have had their formative training, mature trees or wall-trained shrubs do not need much attention apart from some replacement pruning. This involves removing one of the seven or so main limbs every three to four years in March or April, to stop the whole bush becoming too old and unproductive. Apart from this, providing you have the wall space, you can leave well alone. I have seen many such 'neglected' plants, and they still fruit well, although perhaps not as well as they might.

"On the other hand, if you want to maximize your crop (assuming it is against a wall), buy a copy of Clive Simms's Nutshell Guide to Growing Figs (Orchard House) to see how to fan train it against a wall--it is not hard. Once you have established an approximate fan of branches, you can start the ongoing pruning regime.

"Firstly, remove any weak branches in winter. Then, in April, remove the very tips of the main branches, above the developing figs. This will encourage side shoots, which are summer-pruned by cutting back in June to about four leaves. This technique can almost double the crop and bring it forward by a couple of weeks. Do not be tempted to cut back hard in winter, unless you don't mind forgoing a lot of your crop--this will cause lots of new growth but little fruit."

Season All Season
Date 2007-08-30
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Keywords: Failure to flower, Trachelospermum

PAL Question:

I bought an established, white star jasmine perennial vine one year ago. I was told I could plant it in an extremely large pot and expect to enjoy blooms for about 3 years, but it has not bloomed, nor does it have any buds. It has no pests or blight of any kind. It gets full sun in the morning and partial during the day, and full again in late afternoon. It has always had sufficient water. What's wrong? When do they normally bloom? Was I given inaccurate information?

View Answer:

I am assuming the star jasmine is Trachelospermum jasminoides, as shown in this image from Missouri Botanical Garden.

Failure to flower can be due to a number of causes, as described in this link from University of Vermont Extension.

My top guesses for what may be causing the lack of flowers would be exposure to severe cold in the winter, or over-fertilizing with a nitrogen-heavy fertilizer. The light exposure you describe sounds fine for this plant. In the Pacific Northwest, it flowers mainly from spring to early summer. This link to a Seattle garden writer's site has cultural information appropriate for this region (I don't know where you are writing from).

Season All Season
Date 2007-08-29
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Keywords: Screens, Thuja, Juniperus, Viburnum, Hedges, Ceanothus

PAL Question:

I will be having a very overgrown, rarely pruned laurel removed from my back garden. It has been, if a monstrosity, an effective visual screen. The bare area that it leaves is appproximately 40' in length, is atop a rockery, approximately 3' high, and will look up into the neighbor's back hillside, while they peer down at us in dismay. Can you suggest one or several fast growing, shrubby plants or suitable trees that will act as an attractive visual screen? I do not want bamboo.

View Answer:

Here are a few ideas:

Morella californica

Thuja occidentalis 'Smaragd'

Osmanthus delavayi is also a good choice, but it doesn't get quite tall enough--my own hedge, which is pruned at least twice a year, is about 8 feet tall, so if I really let it go, maybe it would be 10-12 feet.

Juniperus scopulorum 'Wichita Blue'

Juniperus virginiana 'Manhattan Blue'

Viburnum tinus

Ceanothus would also be striking, with blue flowers, but you'd need to find the tallest possible species, and they tend to be short lived.

You could plant a mixed hedgerow, which would allow you to include some of the flowering plants you prefer. King Conservation District has more information on hedgerows.

Season All Season
Date 2007-09-13
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Keywords: Ficus carica

PAL Question:

Are fig trees known for being particularly aromatic?

View Answer:

I looked in a large number of our books on aromatic and fragrant plants, and none listed fig (or Ficus carica) in the index. Although the leaves may be mildly aromatic, it is not the usual reason people cultivate the plant, so apparently not much is written on the subject. I found a highly technical scientific article on a study comparing male and female fig trees and fragrance emission. To the best of my understanding, the composition of the volatile emissions and the quantity differed from male to female, and were subject to seasonal and diurnal changes (most emissions during the day, and in synchronization with the need to attract pollinators). What this suggests to me is that the scent of an individual tree may vary considerably.

The following is from general information on figs, from Purdue University's horticulture department. Excerpt:

Leaves: Fig leaves are used for fodder in India. They are plucked after the fruit harvest. Analyses show: moisture, 67.6%; protein, 4.3%; fat, 1.7%; crude fiber, 4.7%; ash, 5.3%; N-free extract, 16.4%; pentosans, 3.6%; carotene on a dry weight basis, 0.002%. Also present are bergaptene, stigmasterol, sitosterol, and tyrosine. In southern France, there is some use of fig leaves as a source of perfume material called "fig-leaf absolute", a dark-green to brownish-green, semi-solid mass or thick liquid of herbaceous-woody-mossy odor, employed in creating woodland scents.

The following information from a 2004 article by Tony Burfield entitled "a Brief Safety Guidance on Essential Oils" indicates that "fig-leaf absolute," as an essential oil, is phototoxic, in other words, will cause skin irritation when exposed to light. For this reason, it is banned from inclusion in perfumes by the International Fragrance Association.

Another site, BoJensen.net, includes "A small guide to Nature's fragrances," describing various essential oils.Excerpt:

"Fig leaves have a characteristic sweet-green fragrance, perceptible when one stands close to the sun-warm trees or by handling the leaves. They have been extracted on a limited scale for perfumery use in Grasse in southern France. According to Arctander, fig leaf absolute is a dark green to brownish green, semi-solid mass or viscous liquid of a delicately sweet-green, herbaceous and somewhat woody odour with a mossy undertone.

"Roman Kaiser, among 200 identified constituents of fig leaf absolute, found a number of olfactorily relevant N-containing trace constituents, one of them 2-isobutyl-4-methylpyridine, characterized by an attractive tobacco-like, green, herbaceous odor. Major odorants were linalool, benzyl acetate, methyl salicylate, beta-ionone and (Z)-3-hexenyl benzoate [137].

"Buttery et al. identified germacrene D as a major volatile component in fig leaves. Other major volatiles were beta-cyclocitral, (Z)-3-hexenol and (Z)-3-hexenyl acetate [129]."

Ultimately, it seems to me that if you want to plant a fig tree with fragrant leaves, you will have to do a sniff-test of your own. In my experience, all fruit--fresh and dried--from the tree is aromatic, regardless of variety, but you may detect more subtle differences. Buy different types of fresh and dried figs at the market, and visit gardens where figs are growing. I'm afraid that's the best I can come up with.

Season All Season
Date 2007-09-15
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Keywords: Polystichum munitum, Pruning

PAL Question:

We leave for about 5 months in the winter and by the time we get back our sword ferns have sprouted and it's hard to prune the old fronds out without cutting off the new ones. These ferns are in a fairly protected area, so I was wondering if it would be okay to cut off the old fronds in October before we leave? Also would it help if we just cut the old fronds and lay them over the plant to help protect it over the winter?

View Answer:

There are some slight differences of opinion on cutting back sword ferns. It might be fine to cut the old fronds this fall and leave them as protection over the winter, but it isn't really necessary to cut them back until early spring, if at all. The local web site for Great Plant Picks recommends cutting sword ferns to the ground in late winter, or only cutting back every 3 years or so on plants growing in poor soil:

Paghat's Garden, another local gardening site recommends only cutting away dead fronds. Excerpt:

It was once believed it was necessary to cut all the fronds off in February immediately before new growth begins, but it is now the recommendation to only trim dead fronds. By April when the fiddleheads are thickly erupting, any of last year's fronds that have lost their beauty should be removed, but only for looks' sake, removing up to as many as all of them. They'll soon enough be replaced by new. Just don't remove the fronds before winter's final frosts, as the reason this fern adapted itself to keeping its fronds green at least until winters' end is to shelter & protect the humping crown from excessive cold or from sunlight in winter when deciduous trees might not adequately shade the rootcrown.

Since your plants are in a protected area, you might be able to go ahead with your October trimming, but really the main reason to trim is an aesthetic one, so it isn't absolutely necessary.

Season All Season
Date 2007-09-27
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Keywords: Prunus lusitanica, Hummingbirds

PAL Question:

I have a very large, mature Portugal laurel hedge. A tree service is coming out next week to see about pruning it. It is February and I heard that Anna's hummingbirds are beginning to build nests in our area. I have a hummingbird feeder near the hedge. So, my first question, is now an OK time to have the hedge trimmed for the health of the plant? Second, am I risking disturbing nests at this time? In addition, if the neighbors cut back a significant amount of hedge on their side of the fence last year, am I safe to cut some of the height now, or do I need to allow more time for the shrub to recover?

View Answer:

According to the American Horticultural Society's Pruning & Training (ed. Christopher Brickell, DK Publishing, 2011), the ideal time to prune Prunus lusitanica (Portugal laurel) is late spring or early summer. However, it can produce new growth easily from old wood, so if a plant or a hedge requires renovation, it shouldn't pose a problem. It's always best to avoid pruning on very hot days. The Royal Horticultural Society website has general guidelines for hedge pruning:

"Evergreen hedges
Formative pruning: In the spring after planting and for the first two years after planting
Maintenance pruning: Each summer"

If you are concerned about disturbing the Anna's hummingbirds, it makes sense in any case to wait until late spring or early summer. See this information on Anna's hummingbirds from Washington NatureMapping Program:

"Nesting: As is the case with other hummingbird species, male and female Anna's Hummingbirds associate only long enough to mate. The female is responsible for construction of the nest and care of the young. The breeding season begins in December and usually lasts until May or June. Females will lay a clutch of only two white eggs and will produce only one brood per season. The hummingbird eggs are roughly the size and shape of a small jellybean. The hatchlings will remain in the nest for three weeks."

Portugal laurel is generally considered pretty tough, but if you are concerned about pruning too much at one time, you might want to wait until it is in the height of active growth. To sum up, it seems best for both the hummingbirds and the hedge to wait a while.

Season All Season
Date 2012-02-16
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Keywords: Beans--Diseases and pests

PAL Question:

I have grown runner beans in the center of England for several years, with good crops and healthy plants, but this year my plants have some sort of disease. The leaves have brown spots which seem to spread along the leaf veins and then over the whole leaf. Some plants are still producing healthy beans, but on some plants the beans have shrivelled and turned yellow. I don't know if these are the same plants with the worst leaf problems as the plants are tangled together too much. I have looked at various websites, but am not sure that any diseases shown correctly match my problem. I would be very grateful if you have any idea as to what it is and how to deal with it.

View Answer:

While I cannot diagnose the problem remotely, your description does sound quite a bit like anthracnose, which is a fungal disease. According to The Organic Gardener's Handbook of Natural Insect and Disease Control by Barbara Ellis (Rodale Press, 1996), this disease thrives in wet, humid conditions. You would see leaves with dark streaks, and black petioles and veins on the underside of the leaves. If this is indeed the problem, plants may be sprayed with sulfur, or you can seek out resistant cultivars next time around ('Espada,' 'Marbel,' Morgane,' and 'Rocdor' are a few).

On the other hand, the yellowing of the seed pods sounds more like bacterial blight, also encouraged by warm, damp weather. If your plants are not forming any new pods, remove and destroy them. Next time you plant, be sure there is adequate space between plants, and perhaps rotating the crop to a different location might help.

Just to give you some basis of comparison, here are links to sites with information about diseases affecting beans:

Cornell University Vegetable MD Online

University of California, Davis Integrated Pest Management

Royal Horticultural Society lists several problems affecting runner beans. There is a fungal disease of broad beans called chocolate spot which sounds a little like what you describe.

Season All Season
Date 2007-09-19
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Keywords: Ficus carica, Pruning trees, Espaliers

PAL Question:

I purchased a fig tree and my property has very limited space. There is an ideal strip of land by the south side of the wall that gets plenty of sun. I read that fig trees should be planted near a south facing wall, but my only concern is how close can it be to the side of the house. The strip of land is only about 2 feet wide and I also read that fig roots are shallow and spread beyond the canopy. I'm worried that the root system would cause damage to the foundation/basement.

View Answer:

The roots of a fig tree may be shallow, but they may spread out as much as 50 feet, and if the soil conditions are right (soft, permeable), roots may go as much as 20 feet deep. I think planting so close to the house is not ideal, unless you were to have a dwarf variety of fig in a container (such as Petite Negri or Negronne). If there are any cracks in your foundation, then tree roots may be a concern. Tree roots do not usually penetrate a solid wall, although as they grow and expand, they can exert pressure on surfaces. The other concern with planting that close is that you will find you frequently need to prune branches away from the house. There is a tradition of growing fig trees as espalier forms (trained to grow flat, on one plane), but to do this you need to restrict the tree's roots in a container. Below are links to information on how to do espalier:

Mississippi Cooperative Extension

Royal Horticultural Society

Reads Nursery Excerpt:

Allow 8' - 15' horizontally and 6' - 10' in height per plant. Root restriction is required. Construct a box of 2' square paving slabs 4' x 2' against a wall or side of greenhouse, leaving 3 inches showing above ground. Put 9 inches of rammed brick rubble in the bottom and fill up with good soil such as John Innes No 3.[*This is a British product--you can use compost instead.] When planting loosen root ball carefully around the outside and plant 1-2"deeper than before. Water in well. Pruning. Treat as for Figs in Pots but, on a wall, the plant should be fan trained on horizontal wires 12 inches apart.

The following links have excellent general information about growing fig trees:

Purdue University Extension

California Rare Fruit Growers

Season All Season
Date 2007-09-19
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Keywords: Organic fertilizers, Soil amendments

PAL Question:

I was wondering if you could provide me with a more or less exhaustive list of organic fertilizers and soil amendments, their nutrient profile, and what they are good for, etc.

View Answer:

When you say 'organic' fertilizer and soil amendments, do you mean those items which are allowed under current organic regulations? I ask because there is considerable difference of opinion over what is meant by the word 'organic' in this context. Sewage sludge which contains heavy metals could be said to be organically derived, but might not pass muster in an organic garden, for example.

If you mean products which are on the Organic Materials Review Institute list of permitted soil amendments, here is a link to their lists.

If you need a truly exhaustive list, I recommend looking at some of the books available in the Miller Library on this subject. Rodale's Illustrated Encyclopedia of Gardening and Landscaping Techniques edited by Barbara Ellis (Rodale, 1990) has a very easy-to-use (but probably not exhaustive) guide to soil amendments and fertilizers. Below are are some other titles:

Soils : the right way to use fertilizers, composts, soil conditioners, soil testing/problem soils 1986

Let nature do the growing : the fertilizer-free vegetable garden / by Gajin Tokuno c1986

Fertilizers and soil amendments / Roy H. Follett, Larry S. Murphy, Roy L. Donahue

Fertility without fertilizers : a basic approach to organic gardening / Lawrence D. Hills

Feeding plants the organic way / Jim Hay

Growing green: animal-free organic techniques / Jenny Hall and Iain Tollhurst

The following links may be helpful to you:

Colorado State University Extension - Organic Fertilizers

National Sustainable Agriculture Information Service - Sources of Organic Fertilizers and Amendments

University of California Santa Cruz Agroecology Program - Building Fertile Soil

Washington State University Extension - Organic Fertilizers

Oregon State University - Improving Garden Soils with Organic Matter

Utah State University Extension

Season All Season
Date 2007-09-19
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Keywords: Malus, Pyrus, Tree identification, Prunus

PAL Question:

Is it possible that I'm seeing cherry trees flowering this early (mid-February)? Some have white flowers, and some are pink.

View Answer:

It is certainly true that things are flowering early due to our mild winter this year. Last year, the famous cherry blossoms in the University of Washington's Quad began opening on March 13, and this winter has been warmer, so they may be opening earlier than that. While it is possible you are seeing flowering ornamental cherries (Prunus species), they are easily confused with their cousins in the same genus, flowering ornamental plums-- extremely common street trees in Seattle--most of which are definitely flowering now. Ornamental pears (Pyrus) are also flowering now. They have white petals, and might be mistaken for cherry trees as well but the distinctive odor of pear blossoms is a big clue to their true identity: acrid, astringent, and just plain stinky!

The Vancouver Cherry Blossom Festival offers some pointers on how to tell the difference between cherry and plum blossoms. Most cherry blossoms are not noticeably fragrant, while plums are. Cherry blossoms usually have small splits or indentations at the ends of their petals. Note, however, that the book Japanese Flowering Cherries by Wybe Kuitert (Timber Press, 1999) says cherry "petals are mostly [emphasis mine] retuse," that is, not all of them have a shallow notch or split on the ends of the petals.

Project BudBurst, a citizen-science phenology project, has information on identifying cherry trees. There is also a guide to telling the difference between cherry and apple blossoms (apple blossoms have 3 to 5 styles whereas cherries have one). According to the British Natural History Museum, one unifying characteristic of cherries is "flowers in clusters with stalks all arising from a central point, or arranged along a short stem, or in spikes."

Season Spring
Date 2015-02-28
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Keywords: Grapes--Diseases and pests, Vitis

PAL Question:

We've got an established grapevine that has acquired erineum mites, and a horticulturist advised us to use dormant spray this fall. The dormant sprays are rather nasty things, and I recently ran across Neem oil, which says it acts as a miticide. It sounds like the concentrated Neem oil is pretty nasty, too, but I'm wondering: (1) will Neem oil work to get rid of the mites; and (2) is it any less harmful to the environment than the traditional dormant sprays?

View Answer:

According to the University of California, Davis Integrated Pest Management program, Erineum mites will not adversely affect your grape crop, they merely cause an aesthetic problem (disfigured leaves).

Washington State University Extension does mention using dormant-season horticultural oils or wettable sulfur. Excerpt:

"The grape erineum mite, Collomerus vitus, is actually a type of eriophyid mite. They are very tiny, whitish, worm-like, and spindle-shaped. Their bodies have definite annulations or rings, and only two pairs of legs directly behind the mouthparts. They overwinter under outer bud scales and feed on leaves during summer. The upper leaf surface becomes blistered, and blisters on the lower leaf surface turn white, yellow, or brown. Colonies of mites live inside the blisters (erinea) formed by their feeding on the lower surfaces. The blisters contain masses of enlarged leaf hairs. Large infestations can cause major stress on young vines. From mid-August to leaf drop, the mites migrate back to the overwintering sites beneath bud scales.

"Apply according to label instructions. Dormant-season horticultural oils or wettable sulfur applications may be helpful."

I have only seen references to serious damage from this pest when the grapevine affected is very young, so you may be able to do nothing at all. Neem's effectiveness as a miticide is as yet unproven, and when selecting a Neem-based product, you have to make sure it actually contains the active ingredient said to affect insects, Azadirachtin--some "Neem" products do not. (Also, Azadirachtin affects good bugs as well as the ones you may be trying to control, so it is definitely not risk-free).

Paghat's Garden website article on the "Myth and Reality of Neem Worship"

Although most horticultural oils are petroleum-based, there are supposedly a few out there which are being made with vegetable oil, which would be a preferable alternative if you really needed to spray for the erineum mites. Colorado State University Extension has an article on dormant oil.

Season All Season
Date 2007-09-19
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Keywords: Betula

PAL Question:

A landscaper planted a River birch next to our house 9 years ago. The roots are everywhere. We heard that this is one of the worst trees to plant next to a house. We have a basement. What should we do?

View Answer:

River birch (Betula nigra) is rated as having moderate root damage potential by the Urban Forest Ecosystems Institute.

The following, from University of Saskatchewan, (scroll down to "Guide to Birch Trees") supports what you have heard about planting this tree near a structure, but takes the approach that it is not good for the tree, rather than a danger to the foundation. Excerpt:

"On a healthy birch, the roots will spread to a distance of at least twice the tree's height. This means that the roots of a mature tree may cover an area about one third the size of a football field. To permit proper root spread, trees should be planted as far as possible from any obstruction that may interfere with root development. Sidewalks, driveways, patios and building foundations will all limit root development. Where a tree is growing on heavy soils, aeration holes will help maintain root vitality."

Tree roots are not likely to infiltrate a solid foundation, but if there are cracks, it is certainly possible, and if tree roots expand sufficiently over time, they may begin to exert pressure on the foundation. However, birch roots are shallow, as indicated in this USDA Forest Service guide to growing birch trees.

It is not a good idea to plant any tree right next to a house, if only because the tree will undoubtedly require pruning to keep it out of the way of windows, doors, and so forth. If you like the tree and would like to move it to a better spot, you should consider contacting a certified arborist. Here are links to referral services.

Plant Amnesty

Pacific Northwest Chapter of the International Society of Arboriculture

Season All Season
Date 2007-09-21
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Keywords: Berberis, Trachelospermum, Euonymus, Taxus baccata, Screens, Thuja, Nandina domestica, Hydrangea, Ilex, Hedges, Clematis, Buxus, Bamboo

PAL Question:

Could you recommend some plants for a privacy screen that are also narrow? These would be planted in front of a fence in our backyard.

View Answer:

Here is some general information on plants for creating a screen.

Trees for Problem Landscape Sites -- Screening from Virginia Cooperative Extension

Good Hedges Make Good Neighbors from the United States National Arboretum

Bet on Hedges by local garden writer Valerie Easton.

Here is a list of narrow plants for a screen from local garden designer Chris Pfeiffer:

Fastigiate shrubs for naturally narrow hedges. Compiled by Chris Pfeiffer. 2005.

Zones 5-6:

American arborvitae 'Rheingold' (Thuja occidentalis 'Rheingold') 5'h x 3'w

Barberry 'Helmond Pillar' (Berberis thunbergii f. atropurpurea 'Helmond Pillar') 6'h x 2'w

Boxwood 'Graham Blandy' (Buxus sempervirens 'Graham Blandy') 8'h x 1-1/2' w

English yew 'Standishii' (Taxus baccata 'Standishii') 4'h x 1-1/2' w

Irish yew (Taxus baccata 'Fastigiata') 20' h x 4' w

Japanese holly Jersey pinnacle (Ilex crenata 'Jersey Pinnacle') 6' h x 4' w

Japanese holly Mariesii (Ilex crenata 'Mariesii') 3' h x 1-1/2' w

Zones 7-9, in addition to the above:

Dwarf yeddo rhaphiolepis (Rhaphiolepis umbellata Gulf GreenTM) 3-4' h x 2' w

Heavenly bamboo 'Gulf Stream' (Nandina domestica 'Gulf Stream') 4' h x 2' w

Japanese euonymus 'Green Spire' (Euonymus japonicus 'Green Spire') 15' h x 6' w

You might also consider installing a trellis to increase the height of the fence, and then growing an evergreen vine such as Clematis armandii, evergreen hydrangea (Hydrangea seemanii), or star jasmine (Trachelospermum jasminoides).

This link is also helpful (scroll down to "Evergreen Vines" and look for appropriate height and light requirements).

You could grow bamboo, but I would recommend growing it in a container, or a series of containers, as you do not want the roots to spread. I have seen an effective bamboo screen between two houses growing in a long rectangular lined wooden trough (lined with bamboo barrier). Some species of bamboo are more tolerant of partial shade than others. Look for a clumping, rather than a running, bamboo (like Fargesia) to be on the safe side.

Growing Bamboo in Georgia

Running and Clumping Bamboos

Bamboos for hedges or tall privacy screens

Season All Season
Date 2008-01-03
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Keywords: Powdery mildew diseases, Nandina domestica

PAL Question:

Can you give me some suggestions on how to treat a Nandina infected with powdery mildew?

View Answer:

Apparently, powdery mildew on Nandina is becoming a common problem in our area, as the article linked here indicates.

While this fungal disease is unsightly, it generally does not kill affected plants. Sometimes improving air circulation around the plant (by pruning congested growth) can help, and making sure to practice good sanitation by picking up fallen leaves affected by the mildew is also important.

There is an interesting idea in this Science News article on using milk powder in water as a spray to control the disease.

Several organic gardening sources recommend a baking soda spray. The Organic Gardener's Handbook of Natural Insect and Disease Control by Barbara Ellis (Rodale Press, 1996) recommends dissolving 1 teaspoon of baking soda in 1 quart of warm water. You can add up to a teaspoon of dish soap to make the solution stick to the leaves more effectively. Here is another source with slightly different recommendations, from the National Sustainable Agriculture Information Service.

More from University of California, Davis. Excerpt:

Shade and moderate temperatures favor most powdery mildews. Locate plants in sunny areas as much as possible, provide good air circulation, and avoid excess fertilizer. A good alternative is to use slow-release fertilizer. Overhead sprinkling may actually reduce the spread of powdery mildew because it washes spores off the plant; also, if spores land in water, they die. The best time to irrigate is in mid-morning so that the plants dry rapidly, reducing the likelihood of infections by other fungi, such as the ones that cause rust or black spot infections on roses. As new shoots begin to develop on perennial plants, watch closely for the appearance of powdery mildew.

Season All Season
Date 2007-09-26
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Keywords: Squirrels, Wildlife pests, Bulbs

PAL Question:

I am trying to plant some bulbs but they are being disturbed and eaten by the squirrels. Do you have any tips and tricks to protect my bulbs from being snacked on?

View Answer:

Here is a 2009 article by Sally Ferguson in the online archive of BC Living magazine on preventing squirrel snacking:

Excerpt:
Q. How do I keep squirrels from digging up bulbs?
A. Squirrels can be terrible pests! They won't bother daffodils and other narcissi bulbs (which taste terrible to them!), but they find tulips and crocus in particular to be worth the effort to sniff out and dig up.
The only sure-fire way to protect tulips and crocuses and other tasty bulb treats from squirrels is to lay wire mesh such as chicken wire on top of the bed. The squirrels can't dig through the mesh and the flowers will grow neatly through the holes.
Bulbs are most vulnerable in fall immediately after planting when the soil is still soft and worked up. Digging then is easy! Squirrels often "chance" upon bulbs when burying their nuts in soft ground. Or they are attracted by "planting debris" such as bits of papery bulb tunics and other bulb-scented bits from the bulb bags. Don't advertise your plantings: clean up and keep those squirrels guessing!

Here's one neat trick that garden writer Judy Glattstein has found to work: after planting new areas, lay old window screens in frames on the ground, covering the newly-worked up soil. The screen weighs enough to foil the squirrel, but allows for air circulation and rainfall. Once the ground has settled, remove the screens and store for future use.

Another remedy that some find successful is to feed the squirrels during the fall and winter. The theory is that the local squirrel population, when offered a handy plate of peanuts or other easy-to-get treats will leave your bulbs alone. At the White House, the gardeners put up six peanut-filled feeding boxes to satiate the furry denizens there -- and reduced squirrel damage on bulb beds by 95 percent! Many gardeners claim success with commercial repellents, but these are often sticky and unpleasant to deal with, or wash away in the rain.

Home remedies include sowing cayenne pepper into the soil or on the bulbs before planting and scattering moth ball flakes on the ground. You will find advocates and detractors of both methods. A favorite Dutch remedy is to interplant Fritillaria imperialis. This tall dramatic plant gives off an odor that squirrels (and deer too, reportedly) find repellent. There is a book on the subject, Outwitting Squirrels, by Bill Adler, Jr. (1988 Chicago Review Press, Chicago, IL). It's aimed at owners of bird feeders, but you may find some helpful hints.

Season All Season
Date 2007-09-26
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Keywords: Woody plant propagation, Transplanting, Arbutus menziesii

PAL Question:

We've lived in the Northwest for years and love madrone trees. Yesterday, we "rescued" two madrone trees from a construction site with the hope of transplanting them to our Seattle garden. After reading more information on madrone transplanting, I don't think it's an easy task. Do you have more information on this subject?

View Answer:

I've seen several references to madrone trees being difficult to transplant. This one is from Wikipedia: "The trees are difficult to transplant and a seedling should be set in its permanent spot while still small. Transplant mortality becomes significant once a madrone is more than one foot (30 cm) tall."

According to Native Plants in the Coastal Garden (April Pettinger, 2002), "Arbutus seedlings do not like to be transplanted because they have a single, long taproot." However, she does suggest they are not difficult to grow from seed by planting the whole berries in fall where you want the tree to be, and pulling up any extra seedlings that arise. According to Propagation of Pacific Northwest Native Plants (Robin Rose et al, 1998), the seedlings will grow only a centimeter a year at first.

Even if the trees aren't looking great, it might be worthwhile to plant them and see if they come back from the roots, as they tend to have an underground burl that can re-sprout after the original trunk dies.

You might also try contacting the King County Master Gardeners, whose phone clinic can be reached at 296-3440.

Season All Season
Date 2007-10-01
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Keywords: Ficus, House plants

PAL Question:

I just bought a Ficus lyrata that was heavily treated with pesticide. As the plant makes my eyes burn, how can I minimize the pesticide residues on the large leaves? Is the citrus-based Veggie Wash appropriate and not harmful to the plant, or is there a better solution? If changing the soil and pot is necessary, does Ficus lyrata like any particular soil?

View Answer:

Without knowing what pesticide(s) were used, it is difficult to say how the residues could be removed. Looking at The Complete Houseplant Survival Manual, I can see that you would do no harm to the Ficus lyrata by washing the leaves with a sponge dipped in soapy water and then rinsing them with fresh water (this is a remedy often suggested for spider mites). Ficus also tolerates insecticidal soap well, so I imagine that the citrus-based veggie wash would not harm the ficus either. Of course, if the plant is making your eyes burn, it makes sense to take precautions to protect yourself while you are working with it--wear safety glasses, gloves, and a mask, and don't continue to work with it if it still bothers you.

Ficus lyrata is not picky about soil, any good potting soil will do, and it is generally suggested that a smallish pot will help keep the plant from getting too big.

Season All Season
Date 2007-10-01
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Keywords: Rosa

PAL Question:

I was wondering if you could send me information about Floribunda roses. I'm doing a research paper.

View Answer:

We have a large selection of books on roses here in the Elisabeth C. Miller Library. You are welcome to come in and browse as well as borrow books.

The Seattle Rose Society says the following about Floribunda roses: Floribunda roses combine the best aspects of their parent plants: the Hybrid Tea rose and Polyantha rose. They receive their flower form and foliage from the Hybrid Tea while taking after the Polyantha in increased hardiness and exuberance of blooms. This link is to their lists of recommended roses for the Puget Sound region, including the best Floribundas.

Brooklyn Botanic Garden has a book entitled Easy-Care Roses, part of which is available on their website. Here is a link to excerpts from this book.

Here are additional links which may be useful.

Roger's Roses

Roses and everything rose & gardening related

American Rose Society

Olympia Rose Society

Most of our books have at least a little information on Floribundas, but none is specifically and exclusively about them. I recommend The Companion to Roses by John Fisher (Salem House, 1987) for history of rose classification, and Jeff Cox's Landscape with Roses (Taunton Press, 2002) for practical ideas on using roses in the garden, and recommendations of specific Floribundas which do well. Cox says that Floribundas are the best of the Modern roses for most landscaping situations because of their hardiness, free-flowering habit, bushy form, and flowering season. They work well both as specimen plants and in combination with other flowers and shrubs in beds and borders. Most grow 2-4 feet tall, and are dense enough to be used as hedge plants. Varieties range from single, semi-double, to double flowers. Some are fragrant. Specific varieties mentioned by Cox are 'Gruss an Aachen,' 'Iceberg,' 'Queen Elizabeth,' 'Marmalade Skies,' 'Showbiz,' 'Betty Prior,' 'Escapade,' 'Nearly Wild,' 'Lilac Charm,' 'Europeana,' 'Sunsprite,' and 'Apricot Nectar.'

Season All Season
Date 2007-09-29
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Keywords: Bamboo

PAL Question:

I recently moved to a property that used to be a bamboo farm. About 1 acre of bamboo remains. It is of the Henon species and about 20-25 feet in height and it appears to have some mite infestation. I want to remove all of the bamboo, and restore the land to native plant habitat. What is the most economical way to remove bamboo and its root clumps? I have hand dug (and burned) a lot of bamboo, but frankly feel overwhelmed by the task at hand because there is still a lot of bamboo on the property. Any suggestions you can offer would be immensely appreciated.

View Answer:

The American Bamboo Society website has information on getting rid of unwanted bamboo, excerpted below. Henon bamboo is a name for a variety of Phyllostachys nigra, which is a running bamboo.

REMOVING A RUNNING BAMBOO

If new shoots of bamboo are coming up all over your yard, it is a running bamboo. To get rid of it, there are four steps:

  1. Cut it off.
  2. Cut it down.
  3. Water the area.
  4. Cut it down again.
  1. Cut it off. All of the culms (stalks) of bamboo in a clump or grove are interconnected underground by rhizomes (underground stems) unless you have cut them by digging a ditch or cutting a line with a spade. A bamboo grove is usually one single plant, not a group of plants. Many people have the impression that every bamboo culm is a separate "tree."

    If the bamboo in your yard has come across from your neighbor's yard, separate your grove from his by cutting the connecting rhizomes, which are usually quite shallow. If you don't, and his part is healthy and vigorous, the rhizomes in your part will still be supported by the photosynthesis in the leaves of his part, and your efforts will be in vain. On the other hand, if you do manage to kill your part with a herbicide you may also kill his part. Lawsuits or at least hard feelings can result.

    Therefore, be sure to isolate the portion you want to keep from the portion you want to kill. Cutting rhizomes with a spade or a saw will do the trick if you do it every year. If the growth is old, you may need to use a mattock or a digging bar the first time. Digging a ditch and putting in a barrier* is a more permanent solution.

  2. Cut it down. Cut the grove to the ground. All of it. If there is any part you want to keep, see (1).
  3. Water and fertilize the area, to cause new growth.
  4. Cut it down again. And again.
  5. New shoots will come up from the rhizomes. Break them off or cut them off with pruning shears. Keep doing this until no more shoots come up. This will exhaust the energy stored in the rhizomes underground. Without green leaves to photosynthesize and produce new energy, they will no longer be able to send up new shoots. The rhizomes will be left behind, but will rot away.

    That's all you need to do. You need a saw, a pair of pruning shears, and patience, and maybe a spade and/or mattock. The widely advertised herbicides don't work well on bamboo, probably because so much of the plant is underground. Since cutting the bamboo down will do the trick, and you have to cut the bamboo down anyway to remove it from your yard, herbicides are a waste of time and money in this case.

The method described above sounds labor--and time--intensive for a large area like yours. However, if you can cut it all down as close to the ground as possible, and then repeatedly mow any new growth, you may be able to kill it. Here is what the USDA recommends:

Eradicating bamboo is accomplished by first removing all top growth, and then destroying the new shoots as they emerge. If the ground is level and the canes can be cut off very close to the ground, mowing is the best way to destroy new shoots. If the ground cannot be mowed, the canes should be cut down and the area plowed to destroy new shoots as they emerge. Several plowings or mowings will be necessary, but the rhizome need not be removed; it will become depleted and die.

This information is from gardening expert Mike McGrath, via a commercial garden supply business, and there is a possibility that his suggestions of sheet mulching the area (also labor-intensive if you have an acre to deal with) or using high-strength vinegar-based products (use extreme caution with these, even though they are 'natural,' as they are still quite hazardous) might help.

Season All Season
Date 2007-10-11
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July 27 2016 15:17:37